Complementary colour generator

Gives the hue 180 degrees from yours. Complementary pairs produce the strongest contrast of any two-colour scheme, which is exactly why they are easy to overuse.

A complementary pair used at equal amounts fights: two colours of similar saturation directly opposite each other create a vibrating edge that is genuinely uncomfortable to look at. The convention that makes them work is a heavy imbalance — roughly 90 percent of one and 10 percent of the other, with the small amount used as an accent. That is why "red and green" sounds garish and a green room with one red chair does not. It is also worth knowing the wheel here is the RGB hue wheel, not the red-yellow-blue wheel taught in art classes, so the complement of blue is yellow rather than orange.