Complementary Colors
Two colors directly opposite on the color wheel. They produce maximum contrast when paired.
Definition
Complementary colors sit 180° apart on the color wheel. When placed side by side they appear more vivid (each amplifies the other); when mixed they neutralize toward gray. Designers use complementary pairs for high-energy contrast (think red-on-green Christmas branding) but rarely at equal intensity — usually one dominates and the other accents at 10-20%.
Formula
Complement of HSL hue H = (H + 180) mod 360.
Example
Red (0°) ↔ cyan (180°). Orange (30°) ↔ blue (210°). Yellow (60°) ↔ purple (240°). Mauve (276°) ↔ chartreuse (96°).