I have been meaning to post this article.

http://www.sciencedaily.com/releases/2008/10/081028074323.htm
Though this might seems obvious—red has been tied to carnal passions and romantic love across cultures and centuries—this study, led by psychology professor Andrew Elliot of the University of Rochester, is the first empirical support for society's enduring love affair with red. Each test confirmed that men are more likely to ask out and spend more money on women when their in red.
Yes, this could be the result of societal "red is sexy" conditioning, but Elliot argues that a man's response to red more likely stems from deeper biological roots. "Red is linked to romance throughout nature," says Elliot