A colour opposite the original colour in the colour circle. Red-green, blue-yellow, etc.
see http://en.wikipedia.org/wiki/Complementary_color
Every color is a complementary color. Complementary means a set of two colors which are opposite each other on the color wheel. Yellow is a complementary color with purple.
According to the principles of color theory in studio art, the complementary color of green is red.
The seven color schemes are monochromatic, analogous, complementary, split complementary, double complementary, triadic, and tone on tone.
yellow
Orange
red
Red
purple
purple!
blue
Magenta.
yellow