Some colorists say that you should grade everything for consistent skin tones, since out of all the elements in the scene, this is the most important for the audience. The argument goes that if skin tones look correct, the rest of the frame can be hot pink or neon green and nobody will bat an eye. Yet skin reflects the environment, and people photographed in a bright desert will look different than people photographed under studio lights surrounded by dark blue/green walls. So I get them consistent for the location, but I don’t worry too much about consistency over the entire film. And besides, as you said, makeup can be inconsistent.