Complements
A color that holds a position directly across the wheel from another is known as a complement. In the world of pigments and color mixing, the color pairs are: yellow-violet, red-green, and blue-orange. When pigment complements are mixed together, they result in a neutral gray, that is, a gray with no hue identity. This is all pretty familiar to anyone who has fooled around with paints.
But in the realm of afterimages, light mixing, and visual perception, the complement pairings are slightly different. Blue is opposite yellow, not orange.
You can see this for yourself with the diagram above. Stare at the middle of the colorful circle for 20 seconds. Then shift your gaze to the middle of the white circle and relax your eyes. The complementary colors should emerge. Note that the afterimage of blue is yellow and vice versa. But if you were to mix that yellow and that blue as paints, you wouldn’t get a gray, you’d get a green. In fact, pigments can behave unpredictably when mixed. Intermediate mixtures don’t always land on the straight line drawn between the two starting colors.
How does this affect the way we design a color wheel? First of all, you have to decide whether you want to try to represent the practicalities of pigments or the behavior of color in an optical or a mathematical realm. In other words, your color wheel must either represent the ideal world of optical color or the physical world of paints, but no single wheel can accurately represent both color universes.
ChromaMany color wheels include the dimension of grayness versus intensity, known as chroma, also commonly called saturation. Here’s the traditional artist’s color wheel I made years ago, which goes to zero chroma at the center.
(By the way, which term do you use? Please vote in the poll at left). "Chroma," a term invented by Albert Munsell, is the degree a color ranges between neutrality and vibrancy or purity.
Tomorrow I'll try to take a look at that question posed yesterday: Are some colors really more primary than others?
Reviewing the posts in this series:
Part 1: Wrapping the Spectrum
Part 2: Primaries and Secondaries
Part 3: Complements, Afterimages, and Chroma
Part 4: Problems with the Traditional Wheel
Part 5: The Munsell System
Part 6: Cyan, Magenta, and Yellow
Part 7: The Yurmby Wheel