Complementary colors are pairs of hues that, when combined, cancel each other out in terms of light. In color theory, complementary colors are opposite each other on the color wheel. For example, red is complementary to green, blue to orange, and yellow to purple. When these colors are placed next to each other in a color image, they can create a striking contrast and vibrancy. This concept is often used in art, design, and photography to create dynamic and engaging visuals.