Experts in color psychology emphasize the importance of brighter colors for young children. Bright colors provide visual stimulation and discourage shyness and passivity. You may wish to choose more than one bright shade and paint walls in different colors. Select colors that go well together, perhaps two walls in sunshine yellow with another wall of brilliant leaf green and the remaining wall bright blue. Red is also a good color, but should be used in moderation to avoid overstimulating children. Orange is best for environments where children are encouraged to take part in physical activity, though it tends to inhibit quiet and concentration.
If the classroom already receives a great deal of light from south or west facing windows, you may want to choose quieter colors as the amount of sunlight can make bright colors too loud. You can choose a relaxing pastel shade, such as lavender or sky blue, both of which promote relaxation. Add an element of brighter color by painting a mural such as rainbow or rain forest scene on the wall which receives the least sunlight.
Green is known to promote relaxation, but too much of one shade of green can become monotonous. Choose a few complementary shades of green to gain the color psychology benefits it offers while still providing the variety that preschoolers crave. You may wish to divide the classroom into different areas, with a brighter shade of green forming the backdrop for playtime and physical activities, and softer shades for areas where you want children to engage in quiet learning.