Colors regarded as being in extreme contrast to each other, the 'complement' of a primary color, either red, yellow or blue, is achieved by mixing the other two primary colors together. For example, the complementary color of red is green, created by mixing yellow and blue. When juxtaposed, complementary colors intensify each other. Complements of intermediate colors, colors between primary and secondary colors, are shown on a Color Circle. Sources: Kimberley Reynolds and Richard Siddon, "Illustrated Dictionary of Art Terms"; Ralph Mayer, "A Dictionary of Art Terms and Techniques" <br><br>Colors at opposite points on the color wheel, for example, red and green, yellow and purple. (See Primary and Secondary Colors)<br><br> Colors which are located opposite one another on the color wheel (e.g., red and green, yellow and purple, blue and orange); colors which when mixed together will (in color theory) produce a neutral color (a color which is neither warm nor cool). In the case of the three primary colors (red, yellow and blue), the complementary of one primary will be the mixture of the other two primaries (complementary of red will be a mixture of yellow and blue, or green). When placed next to one another, complementary colors will make one another appear much more intense, sometimes in an "eye-popping" sense, which was utilized by Op artists of the 1960's to create optical effects. Also in color theory, an object's primary color has its complementary color in its shadows (e.g., the shadows on and around a painted yellow apple will contain some purple).<br><br>Colors that are directly opposite each other on the color wheel, such as red and green, blue and orange, and violet and yellow. When complements are mixed together they form the neutral colors of brown or gray. Note that this term is spelled differently than the word "complimentary," which means gift.Related link: Sanford has a page defining complementary colors. Also see analogous colors, benizuri-e, color scheme, monochromatic colors, split complementary, and triadic colors.