To scan the colour just holds it close to the colour of the object to be scanned and press the scan button. The scanner begins to detect colour after the button is pressed. The RGB cartridge of the pen mixes the required ink to make the target colour. It would require room for mixing ink and another room for storing colours and a scanner to detect colour right? It’s rather unbelievable as technologies have improved that far as all the parts and electronics needed, can be summed to a size of a useful pen.