I have often used Henna hair dye, but how are different colours acheived through it. Surely one plane = one colour. But with henna black, red, brown are available. Is it different parts of the plant? Or do they add something else.......
My understanding was that the root, stem, leaves and seed of the Henna plant all provide different colourings but there's probably variation associated with preparation of the dye as well (roasting, what solvent is used etc)