As a movie character quipped, "Always bet on Black." It's as simple and neutral as you're likely to get. If Black seems too bland, I've seen some people use "Ebony." I think what people are looking for in general are "Dark Skin Textures." Given the variety of actual hues, even within racial and ethnic groups, I think that's a good general description. Let people look at the examples and see if it fits what they're looking for specifically. As long as that's part of the description, any other catchy name you want to add is fine, as long as in, nemesis10 examples, you don't use something obviously in poor taste. Come back here when you've chosen a name, I'm sure someone will tell you in the unlikely event you've somehow goofed.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken