Since red and green make brown, people with red-green blindness often have trouble telling the three colors apart.

WSJ: New Outlook for Colorblindness

In a series of five studies, about 150 heterosexual men (homosexual men and those with red-green color blindness were excluded) rated photographs of women framed in red, white, gray, green, or blue, or with the woman in a red or blue shirt.

CNN: Wearing red may boost your sex appeal

Blue and yellow tones work effectively but not red or green because of canine colour-blindness.

BBC: New TV channel for dogs sets tails wagging in Israel