So many people email me asking about how well henna will show up on dark skin. I've seen some very dark skinned people with the most beautiful mahogany/black cherry colored henna stains.
On some pale people there is a higher contrast of color between the stain and the skin color, so it is more obvious from a distance. But, on the other hand, some people with pale skin don't stain very well, and their stains blend in with their freckles from a distance!
Henna has been used by North Africans for thousands of years, and not just light skinned Arabs from Morocco and Algeria, but also dark skinned people from Somalia with beautiful results.
Here are some pictures of a stunning girl from the Ohio State Fair's Cox Fine Arts Building who's shoulder I hennaed. She has very dark skin, and got wonderful results from her henna.