Color really actually affects a lot.
Red is a stimulating color, and brighter hues can make for a faster heartbeat and higher blood pressure. It can be noticeable and vibrant, or sensual and alluring. Pink, on the other hand, can actually cause people to loose energy.
Blues bring out calming chemicals, and people are more productive in blue rooms -- studies show blue weight rooms help weightlifters lift more.
Green can improve vision, and it is used in rooms to help relax people. It is often associated with nature.
Yellow speeds metabolism and enhances concentration, but is most difficult on the eye. People lose their tempers more in yellow rooms, and babies cry more as well.
Purple can be sophisticated and luxurious, or very romantic. It is not commonly found often in nature, though, so it doesn't stimulate as much beyond that.
Browns and neutrals are not distracting and very natural.
White can show purity and innocence or simplicity, but it can also be a very sterile color. Too much white can be stressful.
Black can symbolize authority or power, or submission and a state of being subdue, depending on how it's used.