I'm thinking of products that (safely, and temporarily) allow anyone to make their skin bright purple. Or blue. Or orange. Or, yes, black or white. I'm thinking that when such products are widely known and used by a sufficiently large percentage of the population, then there will always be enough of a question (is he "really" black, or is that skin dye?) to cause most people to either re-think their assumptions, or at least to apply them a little more cautiously.