Cool colors: blues, greens, and some purples, and colors containing these hues. Associated with grass, water, and ice. Generally restful, peaceful, and soothing. Recede and fade into the background; look smaller. Appear formal and often display a lack of unity.
Warm colors: colors (hues) composed of red, orange, and yellow hues. Associated with warm things like the sun, fire, and heat. Active and cheery, generally evoking warm and happy feelings. Dominate an arrangement and look larger. Generally informal and blend easily with one another. Large amounts can be psychologically irritating.