Adam Alter describes the effect of red on our sexual impulses:
Yes, red seems to derive much of its power from its association with blood. When we’re attracted to someone, our blood vessels dilate and our skin blushes red—but red clothing, lipstick, rouge,
and other forms of reddening make-up also subtly convey the message that we’re romantically interested. Lower order animals show the same effect—the dominant members of many bird and ape species have particularly red faces or especially striking red feathers or facial features. …
[T]here’s plenty of evidence that men and women find potential mates more attractive when those people are wearing red—or even when they appear in a photograph with a red border. Men indicate that they’ll be more willing to spend more on a date when the women in the picture is wearing red than when she’s wearing a shirt of another color. In one experiment, female hitchhikers were more likely to be picked up by male drivers, but not female ones, when they were wearing red t-shirts rather than shirts of one of several other colors.
(Photo of Amsterdam’s Red Light District by Trey Ratcliff)
The Dish 