How does hue affect mood and behavior? Science can offer clues, but the answers are rarely black and white.

To understand the impact of color on the human mind, consider the operating room, says Shashi Caan, chairwoman of the interior design program at Parsons School of Design. Dominant colors in an operating theater don't come from the décor, she points out. They are the red of human blood and tissue and the seafoam green or blue-green of surgical scrubs.

Aesthetics aside, this color combination is unlikely to change. As long as blood is red, Caan says, the complementary colors of the scrubs will serve the important function of absorbing the surgeon's visual afterimage when she briefly looks away from her patient. If scrubs were, say, white like a doctor's lab coat, staring into all that crimson without a visual respite would nauseate surgeons.

Like the surgeon, we are all affected by environmental color. But unlike in the operating room, where the need to maintain sterility demands a minimum of architectural color, the colors in most interior environments can be planned to achieve desired effects. Color can be employed to energize, subdue, inspire, aggravate or stimulate.

Of course none of this is news to design professionals. Fast-food restaurants have used appetite-stimulating orange for decades, while (appetite-suppressing) blue restaurants are as rare as blue moons. Pink, thought to dull aggression, has been used to subdue prisoners in correctional institutions – and players in opposing teams' locker rooms.

For years parents heeded the advice of color expert Carlton Wagner, who cautioned against painting nurseries yellow, because, he said, the stimulating color would make babies cry.

You won't find red walls in your cardiologist's office, not just because he sees enough of it in the operating room, but because the color has been proven to raise blood pressure. Freudian analyst Bruno Bettelheim was rumored to have painted patients blue to quell their anxiety.

Color and Context

For the most part, many of these color assumptions remain intact today, says Leatrice Eiseman, executive director of the Pantone Color Institute. However, she and others caution designers to dig deeper into the science of color psychology and the context of their projects before applying any paint.

"Anybody can figure out that you want soothing colors in bedrooms and more stimulating colors in high-activity areas," says Janet Friedman of Friedman & Shields, a California-and Arizona-based design firm. Though color psychology rules are far from universal, she notes. Just as people have differing color preferences, they also have different physical and psychological reactions to color. Their reactions can be influenced by everything from gender and age to socioeconomic status and heritage – and can be as individual as fingerprints.

For example, a study conducted at the University of Texas found that women experienced more depression in white, gray and beige offices. Men, meanwhile, reported the same feelings in orange or purple rooms. Retailers routinely use color to attract desired customers. "The more money you pay," Friedman says, "the more you expect [store design to include] deep soothing colors," that suggest luxury and invite lingering.

Subdued nursing-home color palettes may be more stereotypical than senior-sensitive, since many seniors are color blind. If they do see color differences, they might be put off by au courant chartreuse – but nostalgic in the presence of vintage peach.

Primary colors have long been a favorite in kids' rooms. Still, Friedman cautions,"If your children tend to be hyperactive, you're going to give them a much quieter palette."

Hispanic interiors are often awash in bright sherbet tones, while many Asians are most comfortable in understated environments. But ethnic preferences aren't so straightforward, Eiseman says. When she went to China, for example, she was told to steer clear of yellow, the color of rulers, because it evokes Mao Tse-tung. The Chinese students Eiseman met either didn't remember or didn't care. They loved yellow.

Color in Flux

Color can be a shape-shifter in different settings. Most designers test colors in their intended environment to anticipate changes that might occur with different lighting. Colors that everyone loved on a selection board can take on a whole new feel in the context of a finished room, Friedman notes. The turquoise-and-yellow combination that looked merely spunky on sample chips can positively vibrate in large doses.

Even memory plays a role in human reactions to color. Green borrows from nature its benevolent effect on most people. But a child scared by a costumed witch's green face may find the color disturbing even as an adult. On the other hand, that response might depend on the particular shade of green. European researchers concluded that color saturation has a greater effect than hue. They found most deep colors to be equally exciting, while dull colors, no matter the hue, were calming.

The translation from the lab to real life, though, can be complicated and tricky. The Baker-Miller pink devised for use in prison cells does have an immediate calming effect, Eiseman points out. However, studies conducted after prisoners adapted to the color found that the effects diminished over time. An Arizona sheriff learned this the hard way. After extended periods in their pink cells, inmates in Maricopa County jails got more, rather than less, agitated, Freidman says. Now the prisoners are issued pink underwear.

As for the yellow embargo on infants' rooms, feel free to break it, Eiseman says. "Wagner just hated yellow," she says, to the extent that he even denigrated those who liked the color, calling them "neurotic." After much searching, Eiseman hasn't found any research that supports Wagner's claims that the sunny color bugs babies.

Color is Subjective

Indeed, too much reliance on external justification troubles Caan, principal with the Shashi Caan Collective. "We need to rely more on intuition," she says. "Life is messy." And too complex to replicate in a lab. "We as designers need to become not only scientists and psychologists but also rational people and artists." That means considering color holistically in the vernacular of the people with whom it interacts and the context of the place where it will be applied.

Teresa Cox, a St. Paul artist known for her exuberant, color-filled canvases, is a case in point. Cox responds viscerally to color, and her artistic experimentation reinforces her intuition. Her studio, which is also her home, is filled with color: a saturated golden-green floor, a deep-indigo wall; not to mention her colorful paintings everywhere. The tension between all these intense and competing hues would overstimulate many people. For Cox, they are like an elixir. When she once tried to create an 8-foot canvas in shades of only gray, black and white, Cox felt uneasy. "I was literally having cravings for color," she says. "I broke out my other paints and started to add red, which gave me an immediate lift."

Just as a few brush strokes of scarlet paint gave Cox a jolt of energy, even a tiny dose of color can profoundly affect a design.

Use the wrong color in the wrong place, and "you'll know it," Friedman says. "Your teeth will start to itch."

Get it right, Eiseman says, and "there is a bell that rings."