The henna plant, lawsonia inermis, contains a red dye molecule called lawsone. When henna paste is applied, the molecule binds with keratin molecules in skin, fingernails or hair.
When the paste is removed, the lawsone oxidizes and within 24-48 hours produces a final color somewhere along the red/brown spectrum.
The final color of any henna application depends on several factors:
On the red/brown spectrum, there actually is a wide variety of shades that henna can produce. Some of the stains I've seen on myself and others could be described as:
Natural henna can never be purple, green, blue, white, yellow, etc. And you've probably heard my rant about so-called black henna. However, the colors produced by the alchemy of henna and human skin tones makes natural henna stand out on its own as a beautiful art form!
However, if you want a mehndi-style design in a color, Blue Lotus Mehndi has beautiful body paints and glitters that are waterproof but removable. :)