Some common paint color combinations include yellow and green, blue and yellow, and red and green. Color combinations that are pleasing to the eye fall in three basic categories: analogous colors, complementary colors or nature-based colors. This is called color harmony.
The human brain can only handle certain color combinations without becoming bored with the surroundings. At the other extreme, certain color combinations over-stimulate the brain to the point where it rejects what it's seeing. Color harmony provides visual interest without the brain going into overload.
A color wheel displays colors in the order they appear in nature, such as in a rainbow. Color harmony uses a 12 part color wheel that has primary, secondary and tertiary colors. Primary colors are those that can't be created by mixing any other colors. Secondary colors are produced by mixing two primary colors and tertiary colors are produced by combining a primary and secondary color.
Analogous colors sit next to each other on a color wheel. This is what makes green and yellow pleasing. Complimentary colors sit opposite from each other. Red is across from green and reddish-purple is across from yellow-green.
Nature-based color schemes ignore the color wheel. For example, flowers with both red and yellow petals are common. The contrasting foliage usually has more than one shade of green. Translate that into a color combination for a room or painting and the result is a multi-colored mix of red, yellow, light and dark greens.