Make-up was any of various chemical agents used for cosmetic and fashion purposes.
While under the influence of the polywater intoxication, Kevin Riley suggested over the intercom that the women on the USS Enterprise should use restraint when putting on their make-up, saying that women should not appear overly made up. (TOS: "The Naked Time")
Beverly Crusher considered the wearing of make-up an affectation. (TNG: "The Quality of Life") When Soren noticed in 2368 that women applied "color" to their mouths, eyes, cheeks and fingernails, while men didn't, she surmised that it was up to women to attract men. While Crusher agreed that men on the USS Enterprise-D didn't wear make-up, she corrected Soren's assumption by saying that they did try to attract women in other, less colorful ways. (TNG: "The Outcast")