I don't ask random people (or even people whom I've known for awhile) about their racial and ethnic heritage. I assume that, if they wish to share it with me, they'll share it with me on their own.

But in the absence of that information, the conundrum becomes which racial descriptors, if any, should be used when referring to random strangers? Or if we should leave skin color out of it altogether, and, instead, focus on other attributes as descriptors when encountering strangers?