We all have natural reactions to color—a clear blue sky can make you feel more peaceful; a bunch of daffodils, more optimistic. So its no surprise that the colors in your home can have an impact on your mood, too. Red, for instance, tends to be stimulating, and blue, calming, says color researcher Nancy J. Stone, PhD, a professor of psychology at Creighton University. How pure and bright a shade is can come into play, too, as well as personal associations with the color. Heres how you can tap into the power of color to feel happier, calmer, or more inspired—without a huge paint job.

Energy: red and violet
These two stimulating colors boost your energy level by causing your body to pump out more adrenaline, says Leslie Harrington, a founder of LH Color, a color-consulting and research firm in Old Greenwich, Conn. One British study found that when evenly matched Olympic athletes competed, those wearing red won significantly more than their blue-wearing opponents. These high-energy colors are especially good in home offices, entryways, small sitting rooms, or staircases. (Avoid them in the bedroom and bathroom, where you want to relax. You may want to skip these colors in the kitchen, too, because energizing hues can boost your appetite.) If you want to feel inspired but not wired, add just a touch here and there—a red-leather magazine caddy or even a big bunch of fresh red or purple flowers, suggests Shane Reilly, a San Francisco–based interior designer.

Happy: green and yellow
Want to feel more upbeat? Bring in the colors of sunshine and spring fields. In a study from the Vrije Universiteit in Amsterdam, adults reported feeling happier around these two colors. Soft or pale yellows are ideal for playrooms and childrens rooms. Add a new rug: Madeline Wineribs Yellow Cotton Stripe rug ($550 for 6 feet by 9 feet) fits any decor. Or paint just the ceiling to create a sunny feel, a favorite technique of New York City–based interior designer Thomas Jayne—try Benjamin Moores Aura in banana yellow ($54.99) and add a lighter-color paint to tone down the hue as desired. Green is an especially good pick to brighten rooms with mostly neutral tones. Toss two celadon-colored throw pillows on a taupe sofa, or display your favorite black-and-white photos in a large bright olive-green picture frame like the versatile 8- by 10-inch Studio Leather Frame from Graphic Image ($124).

Calm: blue
Most of us choose blue as our favorite color, and its really no wonder. Blue is a very soothing hue—its the color of the sky and the sea—and we can all use soothing touches of it in our hectic lives. In one of Stones studies, she found that people who were faced with difficult tasks felt less anxious after they saw something blue. Because the color is relaxing, you can feel free to use it more liberally than happy or energizing colors—it will work well in any room where you long to feel less stressed. Be sure to stick with soft, muted blues, though; the brighter, stronger shades, such as French blue, can actually have a stimulating effect. Try adding a touch of this serene shade where you need it most: near your bill-paying station, perhaps. We like the Porcelain Star Lamp ($295) in pale blue from Williams-Sonoma Home.

To get more home-decorating ideas, check out The Color Design Source Book by Caroline Clifton-Mogg.