The right to mis-define oneself

[bennyboy]

Well, when we say "black," we mean someone who has at least some African DNA, i.e. the African DNA of a few hundred years ago, not some residual DNA from a few hundred thousand.  So I'd say to be "black," you need a non-zero amount of that DNA.  Getting your hair crimped and applying a tanning agent is not sufficient.

Africa is extremely genetically diverse. What about people who have African ancestors but are light skinned? are they black too?

If the African ancestors were black, and not (for example) Dutch or British, then I think they are black in the sense that word is normally used in the U.S. I believe the woman in the OP was representing the NAACP, where "C" means "colored," and does not generally refer to the colors white or pink.