I would hesitate to use skin color as the primary marker for race in physical description, because it's really not all that useful: I've known quite a few black women with skin lighter than mine, and I'm about as pale as it gets. (And as was pointed out apropos Zvi's post, some characters/actors who code as Black - John and Ronon from SGA were the visual aids - are actually the same skin tone as the white actors.) I don't have any good answer as to how to make racial identity clear in fic *other* than through physical description, though, without just saying it outright (or going to even worse stereotypes.)

Obviously there are plenty of black actors whose skin actually is quite dark, though, and that is something I, as an observer, would probably note, but even that can come off wrong in a story.

I don't know. I guess I fall back on the old non-answer of "What would your POV character notice?" and see where that takes me. (With the Leverage characters, actually, I'd probably write a high level of descriptive detail, even of familiar people, because part of what they are is expert observers of their surroundings...)