Funny story: When I was in an art class in college, a professor was teaching us how to mix oil paints. She was mixing a pretty darkish brown color, and said absentmindedly "anyone know what I need to add to this to make a skin tone?"
Black girl in the front of the class says "looks fine to me!" jokingly. Everyone laughs, but the professor kept concentrating and said "no, no... it needs to be a bit lighter."