What Colour is the Henna Stain?

 The natural dye that is released will leave a stain that will shift from orange to reddish brown over two or three days. This change in colour is a result of the dye reacting with oxygen. Occasionally the heavily calloused areas of the body (palms of the hand, soles of the feet) the stain can reach a darker plum like color, but it will never be black. 
Any of my photos in which the henna looks black are simply taken while the paste is still on the skin.

Henna design - paste still on the skin.

Henna Stain - paste has just been removed.

Henna Stain - two days later.

Please note that stain results are very individual and each person will be a little bit different! 

While some people will always want a black stain that "looks like a tattoo" - please note that the only way to achieve a "black" stain is to add chemicals. The most common chemical used is PPD (para-phenylenediamine) which is not approved for use on skin and can cause serious health problems.