Whenever I dyed my hair with a product that contained henna, it turned red. I have spent years dying my hair. I have had it blonde mostly, but my favorite color is my natural dark brown. Now that I am older and the gray is coming in, I appreciate my natural color more than I ever did.
I used henna to dye my hair and it worked great on my hair, but it didn't work out so well on my sisters' hair. We tried dyeing one of my sisters' hair black and it turned Dark blue. We tried dyeing my youngest sister's hair red and it went bright orange. I think the problem was that the two of them didn't wash the dye out well enough and a little bit stayed in overnight. Also, I used metal to heat the water with. Basically, what I learned was to be careful and that everyone's hair is different. My hair is now back to it's natural color but all three of my sisters (the third one's hair turned out the intended color) still have the dye in their hair even though we dyed our hair in October.
I used henna when I was a teenager. My mom was allowing me this because it is a natural hair dye and actually makes your hair healthy and strong. It coats your hair and makes it a little more thick which was a nice thing for my silky thin hair. I loved how it made my hair red, there are tons of different shades ranging from very dark bronze through lighter red shades. I always got complimented about my color. I recommend using a powder instead of shampoo or cream, more messy but gives better results. Don't use metal, especially aluminum utensils when prepping henna, ceramic or plastic bowl are best. Have a plastic cap to cover your hair to avoid drippings. Use tooth brush to distribute henna evenly in your hair.