Red increases the pulse and heart rate, and raises your blood pressure. It increases the appetite by increasing your metabolism, which is why red is such a popular color in restaurants.("color red metabolism" gets hits mainly for People Magazine-level science info, so I don't know how well-established or bunked this is.)
The office across the hall from me just got "natural sunshine" fluorescent bulbs put in. They are much whiter than the regular bulbs, which are reddish-orange. It is causing me to wonder what effect constant immersion in red light is having on office workers. Obesity? Or is the above effect only a differential one? Has this even been studied?
Anyway, my invention: blue-tinted "diet" sunglasses.