Lipstick was a cosmetic product used primarily by females to apply a different color to their lips.
When Captain Jean-Luc Picard first visited the Dixon Hill series on the holodeck he met the fictional character Jessica Bradley who gave him a kiss. Picard still had the marks of her lipstick on when Doctor Beverly Crusher removed it in the observation lounge. (TNG: "The Big Goodbye")
In 2371, Neelix observed that Captain Kathryn Janeway looked wonderful one morning while she was looking for coffee in his kitchen in the USS Voyager's mess hall. Neelix thought one of the things she changed about her look was that she might have applied a different color lipstick. Janeway responded that it was, in fact, the same color. (VOY: "The Cloud")