Lipstick

"Thus when we ask, 'Why are ripe tomatoes red?' we can come up with two different kinds of answers. The proximate cause of the redness can be found out chemically and physically, and it can be said, 'Ripe tomatoes are red because they contain xanthophyll and carotenoid pigments that reflect red light.' This does not address the ultimate cause, that which causes red tomatoes to be selectively favored over tomatoes without red color."

--Biologist Adrian Forsyth in A Natural History of Sex