When some men and women get sexually aroused, they have what we call a "sex flush," or a sex glow, where the skin reddens or turns a pinkish color. It's caused by increased blood flow to the surface of the skin and happens to about 50 to 75 percent of women and 25 percent of men. Warmer weather and lighter skin definitely make a sex flush more apparent.
When a woman has a sex flush, pinkish spots appear on her belly and can spread to the breasts, torso, face, hands, feet, and even all the way to her lady parts. For men, the flush starts at the upper belly and moves up the chest to his face, shoulders, forearms, and back.
This coloration of the skin is nothing to be concerned about and usually goes away after orgasm, but it can sometimes take a couple hours. Actually, a darker sex flush may be a good indication that you or your partner is about to have one outstanding orgasm, so a sex flush is definitely a good thing!
— Additional reporting by Alexis Nordby