Shades and Tones of Colour - Colour Creation using the RGB Code, CYMK, Pigments and Dyes

INTRODUCTION

This is the home page to a series of articles which all look at aspects of colour. Specifically they look at the basics of the RGB colour creation system used in modern visual display systems in computer monitors and in television sets. These pages describe how a subtle change in the intensities and proportions of just three different wavelengths of light gives us the myriad of different shades and tones of colour which make up the world of colour today. These pages will also describe the history of these colours, the origins of their names, and how they were produced in the centuries before visual display units.

On this 'Shades and Tones of Colour' home page, the RGB system and various other colour creation methods will be discussed, and the relevance of colour charts and colour names is considered. The definition of colour terms such as 'shades', 'tones' and 'tints' is explained, and links are also provided to the pages in which specific colours are described.

NB: For this introduction, it will be necessary to begin with a short discourse on the nature of light and colour and the electromagnetic spectrum. If the reader's interest is only to understand RGB colour production in visual display units - the basis of all the colour tones in my 'Shades and Tones' pages - then these opening paragraphs could be skipped.


CONTENTS


  • WHAT IS LIGHT? WHAT IS COLOUR?
  • COLOUR WAVELENGTHS WITHIN THE ELECTROMAGNETIC SPECTRUM
  • DIRECT SOURCES OF LIGHT AND COLOUR EMISSIONS (Sunlight, heat and fire, VDUs etc)
  • INDIRECT SOURCES OF LIGHT AND COLOUR - HOW DO WE PERCEIVE COLOUR FROM ALL MATTER? (Light scattering, refraction, and reflection)
  • COMBINATIONS OF EMITTED OR REFLECTED WAVELENGTHS (How new colours are created by combining wavelengths of light)
  • SUMMARY OF THE INFORMATION SO FAR
  • A BRIEF HISTORY OF MAN-MADE COLOUR (Ancient dyes and pigments )
  • A WHOLE NEW NEED FOR QUICK COLOUR IN THE MODERN WORLD (Developments in visual display and colour printing)
  • 1) VISUAL DISPLAY UNITS - ADDITIVE COLOUR AND RGB
  • 2) PIGMENTS, DYES, PAINTS AND INKS - SUBTRACTIVE COLOUR AND CMYK
  • A CONFUSION OF COLOUR CHARTS AND REPRODUCTIONS (Accuracy of colour reproduction and the naming of colours using RGB and CMYK processes)
  • SHADES AND TONES (Definitions)
  • SUMMARY TO THIS PAGE, AND AN INTRODUCTION TO ALL THE OTHER PAGES IN THIS SERIES


WHAT IS LIGHT? WHAT IS COLOUR?

This is not a physics page, and yet any discussion of colour inevitably must touch upon the physics of light, because colour - in essence - is how the human brain perceives certain wavelengths of light - a particular band of electromagnetic radiation.

Electromagnetic radiation is energy generated by charged particle emissions. These emissions possess wave-like characteristics as they travel through space (and air), and physicists can classify them according to the length of the energy waves they generate - waves which may vary from less than one millionth of a metre in length to more than one hundred metres in length. Indeed physicists can group together bands of energies of similar wavelengths as these have quite similar characteristics. The science behind this is complex, but the terminology of these bands of wavelengths is actually very familiar to all of us. The shortest of all wavelengths - those of less than 10 nanometres* - are called gamma rays and x rays. Slightly longer than these are the wavelengths of ultra-violet radiation. At the other end of the spectrum, the longest of all wavelengths (more than 1 centimetre) are those of microwave and radio transmissions. Slightly shorter are the wavelengths of infra-red radiation.

Of course our eyes are not sensitive to any of these bands of electromagnetic radiation, and until little more than 100 years ago they were all entirely unknown to human beings (though we were aware of their effects, such as sunburning caused by UV radiation). However, between the ultra-violet and infra-red bands there exists an incredibly narrow band which can be detected by our brains via our eyes. We call this narrow band, visible light. One of the greatest wonders of the natural world is that even though our eyes are totally blind to 99% of the electromagnetic spectrum, within this very narrow band of visible light we can detect extremely subtle differences between wavelengths. We perceive these wavelength differences as colour.

* 1 nanometre (nm) = 0.000000001 metre (m)


A visual indication of the range of radiations in the electromagnetic spectrum, and how they are classified by wavelength. Only the extremely narrow band of wavelengths known as visible light, can be detected by the human eye
A visual indication of the range of radiations in the electromagnetic spectrum, and how they are classified by wavelength. Only the extremely narrow band of wavelengths known as visible light, can be detected by the human eye | Source

COLOUR WAVELENGTHS WITHIN THE ELECTROMAGNETIC SPECTRUM

As we have seen above, the visible light region of the electromagnetic spectrum is inconceivably tiny compared to the vast range of other wavelengths in the spectrum - our eyes are pretty puny when it comes to detecting radiation! Visible light spans from the margins of detectable shorter range radiation at about 400 nm to the margins of detectable longer wave radiation at about 700 nm. We interpret the shortest waves of 400 nm as 'violet' coloured light and the longest waves of 700 nm as 'red' coloured light. In between these two extremes are the wavelengths we call blue, green, yellow and orange, but also so many other tones as one colour blends into another.

If each specific wavelength within this visible light region can be detected as a separate colour, what happens when we are exposed to the entire range of visible light wavelengths? That's easy. We perceive the entire visible light band in which all the individual wavelengths are combined together as WHITE light. Red, orange, yellow, green , blue, violet - all together, they make white light. It is only when some wavelengths are filtered out or absorbed, that we start seeing the different colours which remain from white light. (And if no visible wavelengths are received by the eye from an object or substance, then of course we see that as BLACK).

If the end point of light (as far as our senses are concerned) is our eyes and our brains, then next we must think about the start point. It soon becomes clear that there are both direct sources and indirect sources of the light and the colours we see.


DIRECT SOURCES OF LIGHT AND COLOUR EMISSIONS

Where do these charged particle emissions of electromagnetic radiation in general, and visible light in particular, come from? Only a few natural bodies emit sufficient amounts of light to be detected by our eyes - the obvious example being the Sun, which provides almost all light here on Earth. There are also the far distant stars, and of course the energy generated by heat and fire here on Earth, can create light. We also have artificial sources of light emission created by mankind - for example light bulbs and neon strip lights. And in the 20th century, a new form of emitted light came into being - the cathode ray tube. Television. And in even more recent years, the modern computer, mobile phones, sat navs and all related devices which use visual display units (VDUs) have seen a proliferation of sources of emitted light. It is this directly emitted light in VDUs with which these 'Shades and Tones' pages will be primarily concerned, though we must briefly turn our attention to other ways in which we can see light and colour.


1) SOURCES OF INDIRECT LIGHT - SCATTERED LIGHT

Although direct light from the Sun is a combination of all wavelengths, light heading in all other directions is scattered by gas particles in the sky - and short wavelength Blue light is more likely to be scattered into the direction of our eyes
Although direct light from the Sun is a combination of all wavelengths, light heading in all other directions is scattered by gas particles in the sky - and short wavelength Blue light is more likely to be scattered into the direction of our eyes | Source

INDIRECT SOURCES OF LIGHT AND COLOUR - HOW DO WE PERCEIVE COLOUR FROM ALL MATTER?

It is known (and has been known since Isaac Newton's time) that the visible part of the electronmagnetic spectrum is composed of different wavelengths of 'light' energy which we perceive as different colours when these are emitted by charged particles. And to date, all we have considered, is the light emitted by charged particles.

However, clearly, this isn't the whole picture. A brown cardboard box doesn't give off much in the way of charged particle emissions. Nor does a red plastic cup, a yellow banana, a pair of pink socks or a lump of greenish mouldy bread! Yet all these things - and almost everything else we see - has colour. Indeed, as will be readily apparent, the vast majority of objects and other matter which appear coloured to us, are not emitting much at all in the way of electromagnetic energy, let alone visible light.

Clearly it is not just direct emitted light from charged particles which we can see. It is also scattered and refracted light in which the component wavelengths of light are somehow bent and deviated in path by substances or objects so they appear to come from somewhere else, and reflected light, in which wavelengths of light are bounced off almost all solid matter as well as some liquids and gases. This is why we can see everything that exists on Earth, even when it is not generating its own light emissions.

But if all light was scattered, refracted or reflected in the same way, then everything would appear white, the combined colour of all visible light wavelengths. We only see things in different colours because the peculiar characteristics of different substances and surfaces allow some wavelengths of light to be scattered or refracted or reflected differently.

The best example of scattering, is probably the blue sky shown above. Very short wavelengths of light are more easily scattered than long wavelengths. When light from the Sun passes through gas particles in the atmosphere, the short wavelengths - such as blue - are scattered much more than the longer wavelengths, and whatever direction one looks, some of this scattered blue light reaches the eye. That is why the sky is blue.

The best example of refraction is probably the rainbow effect shown below. In the image of the prism (an experiment conducted by Newton), different wavelengths may be refracted or bent by differing amounts when passing through a medium such as a prism of glass. As they are refracted, so the combined wavelengths of White light are separated into the component colours. Exactly the same thing happens when sunlight passes through rain-drops in the atmosphere - creating a beautiful rainbow.


2) SOURCES OF INDIRECT LIGHT - REFRACTED LIGHT

How the colours of light can be separated out when all wavelengths of White light are refracted (bent). Short wavelengths are refracted more than long wavelengths. This occurs in nature when light is refracted through raindrops to create a rainbow
How the colours of light can be separated out when all wavelengths of White light are refracted (bent). Short wavelengths are refracted more than long wavelengths. This occurs in nature when light is refracted through raindrops to create a rainbow | Source

3) SOURCES OF INDIRECT LIGHT - REFLECTED LIGHT

Yellow bananas appear yellow because only yellow wavelengths are reflected into our eyes. All other colour wavelengths are absorbed
Yellow bananas appear yellow because only yellow wavelengths are reflected into our eyes. All other colour wavelengths are absorbed | Source

The best example of reflection is pretty much everything else we see as coloured. When light hits an object, the surface of the object will absorb some wavelengths, but others will be reflected. If, for example, all of the wavelengths except for green are absorbed, then we will perceive the only reflected wavelength; in other words, we will perceive the object as green. Likewise, if yellow is the only wavelength reflected, we will see a yellow object, as in the yellow bunch of bananas here. Within the surface of an object, the substances or chemical structures which will absorb certain wavelengths of light, whilst allowing others to be reflected, are called pigments.


COMBINATIONS OF EMITTED OR REFLECTED WAVELENGTHS

If we look at the wavelengths of visible light reproduced in the image below, we can see all the colours as represented in the best known natural manifestation of the visible spectrum - the rainbow - broadly and traditionally categorised as red - orange - yellow - green - blue - indigo - violet. If one accepts this categorisation, this gives us seven colours. But of course there is also a gradation from one colour to the next, so we can see reddish oranges, but also yellowish oranges, and we can see yellowish greens and blueish greens, and this continuous gradation of colours with changing wavelength gives us a much larger number of colour tones.

But there are still many colours missing from this spectrum. We cannot see pink. Where is brown? Or shades of grey? Indeed, there are all kinds of subtle tones which we cannot see in the spectrum - flesh colour, cream, sky-blue, maroon, lilac, and beige. Clearly, there are many colours which are not spectrum colours, but rather they are colours which can only be created by combining very different wavelengths of visible light together.

We have seen that by combining ALL the colours we get white light, but what if just two are combined - say, red and green, or yellow and blue? What if wavelengths just from opposite ends of the spectrum are combined, but the wavelengths of green are absent? And what if INTENSITY of light is varied? In other words what if the amount of light emitted or reflected in some wavelengths is slightly increased or decreased?

Suddenly it becomes apparent, that in this way we are not merely limited to the seven traditional colours of the rainbow, or even limited to the tones which are produced by gradations between these colours. Suddenly, a whole vast range of additional tones is opened up - these may occur naturally, by different combinations of pigments in natural substances, but all these tones may also be artifically created by mankind. Today we have this ability to combine colours. Indeed, we can create every tone and shade and hue which we can possibly imagine or see in the world around us.


The colours of the visible light band in the electromagnetic spectrum gradually merge and change as the wavelength gradually lengthens from left to right, and from Red to Violet
The colours of the visible light band in the electromagnetic spectrum gradually merge and change as the wavelength gradually lengthens from left to right, and from Red to Violet | Source

SUMMARY OF THE INFORMATION SO FAR

If we can very briefly reprise what we have covered so far:

1) We have seen that light is just one small part of the electromagnetic spectrum of energy emitted by charged particles.

2) We have seen that the different wavelengths of light received by our eyes and brains are interpreted as different colours. If several wavelengths are combined together, then a range of colour tones can be achieved. If all wavelengths are combined together, we see this as White light.

3) We have seen that light may be received by our eyes and brains, not merely directly from the source of the emission, but indirectly by scattering and refraction, and most importantly by the absorption or reflection of light from other surfaces and the chemical structures known as pigments which exist in those surfaces.

A BRIEF HISTORY OF MAN-MADE COLOUR

We have already mentioned the natural pigments which exist in most substances and which allow us to perceive colour. Of course, ever since man first created designs on the walls of his caves, we have utilised these pigments for our own benefit. We learned how to harness plant extracts, ground minerals, and even such innovative material as crushed insects and rotten snails - and we used them either as dyes (soaking cloth in a solution of the pigment) or as paints (applying a surface layer of pigment, dissolved in a solvent such as water, and a binding agent for stability). Originally cave art were produced using reds, browns, yellows and blacks created from powdered minerals and charcoal, possibly mixed with animal substances like blood and fat or egg white. By 1000 B.C paints based on the gum of the Acacia tree had been developed. Earliest written records of dyes come from China c2600 BC. Egyptians used soil pigments for reds and yellows, and heated silica and copper with lime to create the first blues. And in ancient Greece, Plato began to experiment with mixing two pigments together to create a third. Dyeing of wools and cottons in the Roman Empire produced many colours of clothing, some of which (notably purple) were extravagantly expensive. Even at this time, a healthy import and export trade in pigments embracing Europe, North Africa and Asia was developing, but in the Dark Ages, pigment manufacture became something of a lost art in Europe, Elsewhere in the world, civilisations were producing their own colours in their own innovative ways. The Mayans in Central America for example, used cochineal, extracted from scale insects, to create carmine dyes. Around 1500 A.D, Europeans began to experiment once more with pigment production, utilising home grown plant dyes and minerals, and new colours imported from the Americas and Asia. Scarlet became the 'new' purple - a luxury dye extracted from a Mediterranean equivalent of the Mayan scale insect. Commercial growing of dye plants would soon expand the market by reducing the cost of dyes, and the Industrial Revolution would introduce mechanisation and efficiency into the production process. It also allowed the development of a new range of synthetic pigments, more stable in structure and cheaper to produce. The first of many in the second half of the 19th century was 'Mauveine' (mauve) in 1856. Paints, previously the preserve of the rich, and not widely used for decorating the walls of domestic dwellings, became more available with the incorporation of linseed oil as an inexpensive binding agent for the pigments. In the 1870s, the first washable paint - Carlton White - was produced, and many more were to follow soon after. By the 1880s, many different colours were available in tins for commercial sale. Further improvements in chemistry of paints and dyes continued in the 20th century with the introduction of such products as fast drying water based acrylics, polyurethane and epoxy paints - methods of applying pigment to suit almost any purpose.


Almost any purpose, but not all the purposes required to meet the needs of modern society. Which brings us to the next section ...


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A WHOLE NEW NEED FOR A QUICK MULTIPLICITY OF COLOURS IN THE MODERN WORLD

Over the millenia natural pigments from plants, animals, minerals and soil have been used to create a range of colours, and in the past 150 years, synthetic sources of these pigments have enabled a vast range of new colours to be artificially created.

But modern life has seen the need develop for a whole new range of subtle uses of colour - both in the rapid printing or photocopying of diagrams, text and photographs, and also in visual display units with the advent of electronic means of communication and ever-changing images in televisions, computers, sat navs and other modern devices. None of these are broad canvases requiring single colour applications, or paintings in which each colour tone can be individually applied. Rather, they require very fine and subtle changes in colour tone and shade, and revolutionary systems of generating all those colours accurately and rapidly. It's no longer good enough for every picture or pattern or image to be painstakingly created by an artist - it has to be done easily, and it has to be mass producible. The next two sections look at just two examples of such colour production systems, which are employed in these new methods of imaging. They may well be new methods of creating colour, but they employ the two age-old natural sources of coloured light described earlier - the direct light of generated electromagnetic radiation, and the indirect light of absorption and reflection.

First we look at direct colour creation - the 20th and 21st century phenomenon of the visual display unit and the best known 'additive' colour system in this field - RGB. Then we look briefly at indirect colour creation - the creation of colours through the use of natural or manufactured pigments and the best known of 'subtractive' colour production systems in this field - CMYK.


These cathode ray tube representations show the  red, green and blue phosphor dots of RGB. Each group of three dots makes one pixel. Light emitted from each dot can be varied in intensity to create many different colours
These cathode ray tube representations show the red, green and blue phosphor dots of RGB. Each group of three dots makes one pixel. Light emitted from each dot can be varied in intensity to create many different colours | Source

1) VISUAL DISPLAY UNITS - ADDITIVE COLOUR AND RGB

In modern visual display units, visible light is generated electrically. There are many ways of doing this. In the traditional cathode ray tube (CRT) of televisions and computer monitors, electrons fired through the tube strike and produce light in millions of tiny phosphor dots of different colours grouped together into picture elements or 'pixels'. In modern plasma screen technology, a similar process of phosphor light generation is utilised, though the mechanism of exciting the phosphor to emit light is different, involving electrically charged plasma. Liquid crystal displays (LCD), so commonplace today in so many devices such as calculators, sat navs, iPads etc as well as flat screen TVs, employ a rather different method involving polarisers and liquid crystal screens of coloured cells, and the filtering of certain wavelengths of generated light to produce specific colours. The precise mechanisms of CRT, plasma and LCD are beyond the scope of this page though many excellent guides to the physics behind these three systems can be found on the Internet. Suffice to say here, however, that they all employ generation of light to create moving images of great complexity by varying the intensities of different wavelengths of visible light emitted from each pixel.

In practice, it is really not necessary to use the entire band of visible wavelengths of light to create a sufficiently wide range of colours as can be discerned by the human eye. Instead it has been found in all of these systems that combining emissions of just three wavelengths - those of Red, Green and Blue light (RGB) - in different proportions and intensities, is sufficient to do the job, and this is the principle behind the RGB colour model. So in visual displays which use RGB, millions of pixels are utilised in which the three 'primary' colours of red, green and blue light are adjusted to create all other colours - we of course cannot see each individual pixel; we just perceive as a new tone or shade, the end product of the proportions of red, green and blue light emitted. As we know, if all wavelengths of visible light are generated together at maximum intensity, then any 'image' created will be seen as WHITE. In RGB, simply combining three such wavelengths from either end of the spectrum (red and blue) and from the middle (green) is enough to achieve this. On the other hand, if no wavelengths are generated, then we see will any image created as BLACK.

This is simple enough, but by omitting just one or two wavelengths, or by subtly varying their intensity, then all the thousands of different hues we can distinguish with the human eye, can also be created.

A need exists to codify the proportion of red, green and blue light required to produce these many hues. These proportions can be described in many ways. Most often, values between 0 and 255 inclusive are used to describe the intensity of each colour component incorporated in a particular tone (because 256 is the total number of different intensities of a colour possible in a single 8 bit byte). It is not very easy however to simply compare such ratios. In my pages, therefore, these values are converted into percentages, which are perhaps easier to compare and contrast. The maximum intensity of each wavelength (red, green and blue) which can be emitted by a pixel will therefore be 100%. If maximum intensity of all three colours is emitted, then the adding together of all three makes increasingly bright light, and ultimately, WHITE light. Therefore RGB is known as an 'additive' process.

Under this system therefore, the table below shows a few selected values, and how we perceive the end colour produced. The image then gives a visual interpretation:


SIMPLE EXAMPLES OF RGB COLOUR COLOUR COMBINATIONS AND CODING

RED
GREEN
BLUE
END COLOUR
100%
100%
100%
WHITE
50%
50%
50%
MID GREY
0%
0%
0%
BLACK
 
 
 
 
100%
0%
0%
BRIGHT RED
0%
100%
0%
BRIGHT GREEN
0%
0%
100%
BRIGHT BLUE
 
 
 
 
100%
100%
0%
YELLOW
100%
0%
100%
MAGENTA
0%
100%
100%
CYAN
The three primary colours of RGB and how combining two of the colours produces a secondary colour. If all three are combined, then all light is reflected, resulting in a white hue
The three primary colours of RGB and how combining two of the colours produces a secondary colour. If all three are combined, then all light is reflected, resulting in a white hue

On all my pages these codes will be presented in the format:

  • X% (R) : X% (G) : X% B.

The examples in the table above are the most basic colours produced by this method. Two colours related to red - orange and pink - will help to demonstrate this further:


100% (R) : 0% (G) : 0% (B) = RED

We have already seen that the above code relates to bright 'pure red'. (As the intensity of red light is reduced from 100%, then the shade of pure red will become progressively darker).

100% (R) : 50% (G) : 0% (B) = ORANGE

In this example we have maximum 100% intensity of red light and 50% intensity of green light. We have seen in the table and in the diagram above how red and green combined in equal proportions makes yellow, but the greater intensity of red light here clearly moves the end tone towards the red end of the spectrum. In other words, this code represents yellowish red or 'orange'.

This example is clear enough, because it deals with only two primary colours in intensities of 100% or 50%. But if all three primary colours are mixed, and in different proportions, so a whole vast range of tones can be created:

100% (R) : 50% (G) : 50% (B) = PINK

In this example, red - at maximum intensity - remains the majority colour with green at 50% intensity. But notice how a considerable intensity of blue light has also been added. As we have seen, as the intensity of all primary colours is increased closer to 100%, so the end shade becomes progressively paler, or closer to white. Therefore this code represents a whitish red or 'pink'.


The three secondary colours of CMYK and how combining two of the colours produces a primary colour. If all three are combined, then no light is reflected, resulting in a black hue
The three secondary colours of CMYK and how combining two of the colours produces a primary colour. If all three are combined, then no light is reflected, resulting in a black hue

2) PIGMENTS, DYES, PAINTS AND INKS - SUBTRACTIVE COLOUR AND CMYK

Next we will look at the CMYK colour system familiar to most of us due to its use in printer ink. If we wish to create colour on a sheet of paper, then we must use pigments or dyes in the form of ink. One fortunate characteristic of modern inks is that - just as in visual display units - by combining just three ink colours together, it is possible to create a wide range of other colours.

The three ink pigments required to produce all of the colours identifiable in - say - a printed photograph - are Cyan, Magenta and Yellow. Thus - CMY. You will see from earlier that these are the 'secondary' colours of RGB, each produced by combining two primary colours at full intensity. In turn, combining two CMY colours on a printed page creates one of of the primary colours as shown in the diagram here. CMY is therefore effectively the exact opposite of RGB. This is because CMY is a 'subtractive' rather than an 'additive' process; pigment layers don't generate light - they 'subtract' light by absorbing certain colours. The cyan pigment absorbs reddish wavelengths of light. The magenta pigment absorbs greenish light, and yellow pigment absorbs blueish light. if two inks are overlaid (eg: cyan and magenta), then both red and green are absorbed, and only one primary colour is reflected and seen by the eye (in this case blue).

The nature of this process is such that white paper has historically been used for colour printing (as opposed to the black screen used for TVs and monitors). Each time one of these inks is added, additional wavelengths are absorbed by the ink pigment - in other words, they are subtracted from the overall whiteness of the final image. If all three inks are employed, then theoretically the final image is BLACK. In practice, imperfections in the pigments means that pure black is difficult to achieve. It is also very expensive to achieve as so much ink is required to absorb all the light, so often a fourth black (K) pigment is also used. Thus we have CMYK inks.

Because no light is actually generated by CMYK pigments, the colours produced do vary a bit according to the ambient light in which the finished print is being viewed (daylight, tungsten lighting etc). Nonetheless, CMYK, like RGB, must be credited with providing modern society with great benefits in accurate reproduction of images and photos in all the shades and tones we could wish for.

In my 'Shades and Tones' pages, I will use the coding system detailed earlier to codify colours. It will be applied to the RGB system as this is the system under which most people will view the pages on monitors. However, reference may also be made to CMYK and to how similar colours may be produced on paper.


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A CONFUSION OF COLOUR CHARTS AND REPRODUCTIONS

Unfortunately although we can now conjure up colours in an instant, there is no standardisation of these shades and tones, and indeed never has been. Pigments even when first ground out of the earth or extracted out of plants thousands of years ago would have varied in concentration. And today one of the problems inherent in the describing of colours is that different colour creation processes create shades which just don't match exactly. We've already seen that the combinations of colours used to create a particular hue will differ under RGB and CMYK, and slightly different tones result when you attempt to copy from one process to the other - anyone who prints a picture straight from a web page will appreciate the difference; a magenta colour on screen, will often not be faithfully reproduced by ink on paper.

Not only is there a big difference between colour creation methods, there will also be big differences in reproduction between different visual display units, and between individual printers and paper types.

Adding further to the confusion is the fact that a single colour shade may be given many different names, whilst the same name may be applied to many different shades, particularly in the fields of advertising and commerce. For example paint manufacturers will employ a whole host of names of their own choosing in order to describe their range of hues. And a brief glance at any website which attempts to lay down as Gospel a system of colour shade labelling will reveal the enormous and slightly ridiculous complexity of describing a colour with any degree of authority. The trouble is, there is no 'colour tone police' to legislate and control the naming of such things. Basically, you can name a colour whatever you like.

On my 'Shades and Tones' pages, I have used RGB to compare different colours, and I've used percentages of colour intensity which seem to me to give the rendition which is most closely associated with a particular tone. It is by no means definitive, but I think that these descriptions of shade and tone could be generally accepted.


THESE ARE 'SHADES' OF GREEN

25% INTENSITY 0% (R) : 25% (G) : 0% (B) - This is pure DARK GREEN (ie: 25% intensity green light with no red or blue contribution)
25% INTENSITY 0% (R) : 25% (G) : 0% (B) - This is pure DARK GREEN (ie: 25% intensity green light with no red or blue contribution)
50% INTENSITY 0% (R) : 50% (G) : 0% (B) - This is pure MID GREEN (ie: 50% intensity green light with no red or blue contribution)
50% INTENSITY 0% (R) : 50% (G) : 0% (B) - This is pure MID GREEN (ie: 50% intensity green light with no red or blue contribution)
100% INTENSITY 0% (R) : 100% (G) : 0% (B) - This is pure LIGHT GREEN (ie: 100% intensity green light with no red or blue contribution)
100% INTENSITY 0% (R) : 100% (G) : 0% (B) - This is pure LIGHT GREEN (ie: 100% intensity green light with no red or blue contribution)

THESE ARE 'TONES' OF GREEN

PALE GREEN 60% (R) :100% (G) : 60% (B) This is Green light with the addition of Red and Blue light in equal proportions, making the final tone paler, and closer to White.
PALE GREEN 60% (R) :100% (G) : 60% (B) This is Green light with the addition of Red and Blue light in equal proportions, making the final tone paler, and closer to White.
YELLOW GREEN 70% (R) : 100% (G) : 0% (B) This is Green light with the addition of Red light. Red and Green together makes Yellow, so this is Green with a distinctly Yellow tint
YELLOW GREEN 70% (R) : 100% (G) : 0% (B) This is Green light with the addition of Red light. Red and Green together makes Yellow, so this is Green with a distinctly Yellow tint
BLUISH GREEN 0% (R) : 75% (G) : 45% (B) This is Green light with the addition of Blue light. Green and Blue together make Cyan, so this is Green with a distinctly Cyan tint
BLUISH GREEN 0% (R) : 75% (G) : 45% (B) This is Green light with the addition of Blue light. Green and Blue together make Cyan, so this is Green with a distinctly Cyan tint

SHADES AND TONES

In this article I have liberally used the terms 'shade' and 'tone' to describe changes in colour. Unfortunately just as a single name may be applied to different colours, so terms like 'shade' and 'tone' may be applied in various ways by different authorities, and may with other terms ('tint', 'pastel' or 'hue') have very specific meanings to artists which are not quite the same as the meanings in general usage. Often the terms are ambiguous, and may sometimes be interchangeable.

'SHADE' is often used to refer to a darkening in intensity of a colour. Its antonym would be 'tint' used to refer to a lightening in intensity. But these definitions create all sorts of problems when comparing wavelengths of red, green and blue light in very different proportions. In my pages 'shade' will generally be used for any change in the intensity of light, and therefore how dark or light a particular colour is. So for instance 100% intensity of green light is pure green, and very bright. 50% intensity of green (without any red or blue light added) is still pure green, but it is a different, darker shade of green.

'TONE' in RGB descriptions usually refers to the actual combination of colours which make up the final hue, and the proportions of each colour within that hue. It therefore refers to the degree of redness or greenness or blueness in the final mix. Most of the colours represented in my pages by this definition are actually 'tones', as they are created by the combination of red, blue and green light in different proportions. The illustrated examples here give an idea of the way these definitions of shade and tone work in practice.

Of course, distinctions between shades and tones are not always obvious, and both may be applicable - for example, in the illustrations given here, yellow green is clearly lighter in shade but also yellower in tone than the dark green colour shown first. It is therefore both a different shade, and a different tone. I will commonly use 'shade' as a general term, though 'tone' will be applied if a clear distinction exists.


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SUMMARY TO THIS PAGE, AND AN INTRODUCTION TO ALL THE OTHER PAGES IN THIS SERIES

This page acts as the introductory page to all my 'Shades and Tones of' articles.

It has not been easy to write this page. I did not want to include too much physics in what is essentially a page about the art of combining colour. Equally the ambiguity of different colour terms does not make it easy to refer to shades, tones, or particular colour names, as others will interpret these quite differently to the way I have done. However, I hope that I have adequately explained the methods which I have used to describe different colours in my 'Shades and Tones' series.

In all my other pages, I avoid anything more than the most basic physics. The intention of these other pages is to take specific colours - red, purple and mauve, green, etc - and show how different combinations of colours on a visual display unit create different shades and tones. I also look at the historical production of these colours in the form of dyes and pigments, the naming of different shades and tones, and their value and meaning to mankind, down through the ages.


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ALL OF MY WEB PAGES

Greensleeves Hubs on HubPages

In addition to pages about colour shades, I also write travel guides and film reviews, articles about science and astronomy, essays in creative writing and pages on many other subjects. If you like this page, please check out my profile page which includes descriptions and links to all my other pages.

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I'D LOVE TO HEAR YOUR COMMENTS. MANY THANKS, ALUN 7 comments

Mayray 3 years ago

Thanks for this resourceful article. You're the best.

University of Nigeria

http://unn.edu.ng


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Greensleeves Hubs 3 years ago from Essex, UK Author

Daniel; when I was young, it always used to puzzle me how in the world of paint, yellow, red and blue were considered the primary colours, and yet in light, green is a primary colour which combines with red to create yellow. So it's been enjoyable researching the nature of colour generation in the various different media.

Computer generated art is very much a growth area in which almost anything now seems to be possible, so I'm sure that will be a very rewarding art form to pursue.

Your comments are much appreciated. Alun.


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Danieljohnston 3 years ago from Portland, Oregon

Having moved from conventional painting to computer generated art processes - IE Photoshop + 3D Models - I was immensely curious about WHY it was so much different from the Cyan Magenta Yellow. Thank you for your clear and concise explanations! I now have some great conversation starters with fellow creators!


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Greensleeves Hubs 3 years ago from Essex, UK Author

justom; Gosh, thanks for that! Really grateful for one of the most flattering comments I've received on my hubs. I do try to take a lot of time over presentation of my hubs to make sure they're as good as I can make them, so as I said to fossillady below, it's really rewarding when that effort is appreciated. And from a photographer and screen printer, it's especially nice to read your comments on this subject. Thanks Tom.

I mention in the hub about how we perceive visible light as different colours - I really think it is one of the seven 'scientific wonders of the world', how our brains can almost miraculously interpret the pure physics of electromagnetic waveforms in such a beautiful visual way as colour. Alun.


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Greensleeves Hubs 3 years ago from Essex, UK Author

Fossillady; I'm really grateful for such a nice comment Kathi. The article ended up being longer than I'd intended, because there's so much that can be said on the subject, and because I wanted to adequately explain the coding in my other 'shades of colour pages'. (Even so I had to miss out lots of stuff about the way colour is produced by LCDs, plasma TVs etc, as well as methods of paint mixing, crayon composition etc). Nice comments like yours make the effort seem worthwhile. Much appreciated. Alun.


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justom 3 years ago from 41042

Having been a photographer for about 40 years and a screen printer for 25 I can't even put into words just how good this hub is. It's so unusual to see this kind of quality writing on HP's that I'm just in awe. I don't know much about nominating hubs for awards but if I did this would be considered THE best I've read on here ever. Whew!! Wonderful work!!


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Fossillady 3 years ago from Saugatuck Michigan

Amazing volume of information and explained well. I didn't get through all of it as it is very technical and interesting, but will come back again. Beautiful body of work with the added illustrations being very helpful! Thanks for sharing, Kathi :O)

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