The labia minora enlarge by two or three times their normal diameter. They also, as both Masters and Dickinson observed, change color, turning pink, bright red, or, occasionally, in women who’ve given birth, a deep wine color. In all of the 7,500 female sexual response cycles that Masters and Johnson watched, no woman who had an orgasm failed to display this “florid coloration” just beforehand. If a man wants to know whether a woman is faking her orgasms he could, barring some logistical hurdles, look for this “sex-skin reaction.”
