I'd agree with those who say contrast is the most important thing. As I cover her with black paint, or mud, or molasses, my wife has occasionally asked me "Did you really just want to marry a coloured girl?!" to which my reply is always that that's not what's it's about, and if her skin was dark I'd be covering her in something light coloured instead.

Having said that, black does look particularly dirty, and as such does perhaps seem a little more exciting than lighter colours...

For gunge, my favorites are black and white.