Colors positioned directly opposite one another on the wheel have the most contrast. These are called complementary colors. Complementary pairings are brilliant, intense and eyecatching. Blue paired with orange would be an example. As colors get closer to each other on the wheel, the more soothing their effect when combined.
Triadic combinations involve three colors.
Colors that are equidistant from each other on the color wheel, such as yellow, blue and red form a triadic combination. Triadic color combinations are generally pleasing to the eye, and become important whenever more than two colors are being considered. By bearing in mind how colors work together, you can achieve the effect you want. There really is no such thing as a wrong choice so long as it pleases you. She adds, however, that there are some tips to follow to get the most pleasing color impact in your spring garden.