complementary color

Meaning: Red, green and blue are the additive primaries. Red + green looks yellow, green + blue looks cyan, and red + blue looks magenta. Because all three primaries together give white, each secondary color pairs with the primary it lacks: yellow with blue, cyan with red, magenta with green. Colored objects and filters work by subtraction. They absorb some wavelengths of white light, and the light that remains is what you see. A material that absorbs red looks cyan.

On the MCAT: A passage describes a filter, pigment or object lit by white or colored light, and you predict the color seen. A yellow object reflects red and green, so under blue light it has nothing to reflect and looks dark. White light through a magenta filter leaves red and blue, so the filter absorbs green.

Common confusion: Mixing lights is not the same as mixing paints. Blue and yellow light add to white, but blue and yellow pigments each absorb light, so the mixture is dark or greenish. The artist's red-yellow-blue wheel also pairs colors differently (red with green, blue with orange). For physics questions, use additive light and ask which wavelengths are absorbed and which reach the eye.