Yeah that's what you think... but when you see a person first time there's no way to tell if someone has naturally pink cheeks, darker lips, long eyelashes and dark eyebrows or not, because you know, there are natural differences.
You can only know for sure when someone is NOT wearing makeup, then they look like they're just out of hospital or from a really poor family or just clinically retarded (this only counts for some people, most are okayish without it too).