Why Henna / Mehndi Colour Different On Everyone

Body Temperature:  Henna colour is depend on body temperature. Some people are naturally more warm blooded than others. The warmer the henna paste and skin is kept, the better the color will be. Henna has the tendency to draw heat out of the body. Doing henna on a hot day is not only a relaxing thing to do, but it also will help to keep you cool. On a cold day though, you may feel as if your skin has turned cold.

How Long Henna kept: The longer you leave on henna design, the darker the design will turn out. If you can, leave it on over night, it will be better colour. If you can not leave it on overnight, try to keep it on for at least 4, preferably 6, hours.  

Skin Type: Someones henna turn out a nice deep red, and almost a black on other person. Its depend on softer or thicker your skin. The more thicker skin the henna will absorb into it. Likewise, that is the reason why henna turns out so light on areas of the body other than the palms of your hands or the soles of your feet.