The most relaxing colors are generally believed to be cool shades such as green and blue. Designers, psychologists, feng shui experts, and advertisers all agree that blues and greens make us feel calm, balanced, and less emotional. They use these hues, especially a sage green, in hospitals, test centers, and television stations to ease nerves and attenuate harsh emotions. Whether this reaction has to do with the effect of wavelengths on brain chemistry, linguistic associations, cultural meanings, or coincidence, has yet to be fully determined.
Interior designers noted that people consistently describe rooms painted blue and green as relaxing and harmonious, a finding that has been backed up by scientific studies. Architects and painters use colors from the cool part of the spectrum like blues and greens on walls and ceilings in bedrooms and bathrooms where people like feeling peaceful.
Driving down any highway in the United States, you'll notice that every sign noting an exit or interchange is comprised of reflective white letters on a chalky, dark green background. Civil engineers determined that a driver's eyes don't get as tired looking at print on a green field, yet the colors provide enough contrast for easy character recognition. Another place we see green used is in the "green room" of theaters or television studios because nervous performers are quieted by the color. This is also the reason surgeons wear green scrubs. Hospital waiting rooms, psychiatric wards, and prison cells often paint their walls green for the same effect.
Scientific researchers in neurology, psychology, and ophthalmology actually have found some preliminary evidence that the relaxing effects of green do not solely depend on cultural associations with leaves or meadows. Our eye perceives color using tiny sensors called cones. Certain cones are sensitive to red or green or blue light. However, overall they are the most sensitive to wavelengths at 510 nm, which translates to green light. Researchers hypothesize that this sensitivity to green objects might affect hormonal production or the circulation of neurotransmitters that in turn influence mood.
Chromotherapy goes back to ancient Chinese and Egyptian practices of using different colors to heal medical problems. Recent studies have shown that when exposed to green colored paper or placed in a green room, a person's heart rate drops, blood pressure lowers, and muscles relax, while hot colors like red or orange cause these values to rise. There is some scientific backing, after all, to the idea that green is the most relaxing color.