The color you use for an interface can trigger a distinct response from people. Everyone associates colors with different things, but colors can also cause an emotional response. Sometimes colors can even have a physical effect on someone!

Black: Gives feeling self-confidence, power, and strength.
Blue: Calming, lowers blood pressure, decreases respiration.
Green: Soothing, relaxing mentally as well as physically, helps those suffering from depression, anxiety, nervousness.
Violet: Suppresses appetite, provides a peaceful environment, good for migraines.
Pink: Used in diet therapy as an appetite suppressant, relaxes muscles, relieves tension, soothing.
Yellow: Energizes, relieves depression, improves memory, stimulates appetite.
Orange: Energizes, stimulates appetite and digestive system.
Red: Stimulates brain wave activity, increases heart rate, respiration and blood pressure!

When the brain registers a color, it automatically tags it to a subconscious response. A red logo is not going to give your viewers a heart attack, but if used excessively it definitely may stimulate your audience (for better or worse).