How we name and separate the colors on the color wheel is a subject with roots in physical science, visual perception, and artistic tradition. That’s what I’d like to explore over the next seven posts. The color wheel is our mental map of the color universe.
This may seem like boring review, but if you read all the posts this week, you may end up completely rethinking the color wheel—at least that’s what happened to me.

When white light is bent or refracted by a prism or a rainbow, it separates into a continuous gradation of colors. Within that smooth spectrum, there’s no clear division between the colors. Sir Isaac Newton (1642-1727) proposed wrapping the spectral colors around a circle by merging the two ends, red and violet. The result was a hue circle, better known as a color wheel.

Newton observed that the hues gradate smoothly into each other. But in his diagram he identified seven colors we’ve come to know as ROYGBIV (red, orange, yellow, green, blue, indigo, and violet). The tradition among artists has been to drop the indigo and to concentrate on six basic colors.
Tomorrow we’ll look at the colors that Newton and his contemporaries called “primitive” and which we call “primary.”
--------
Reviewing the posts in this series:
Part 1: Wrapping the SpectrumPart 2: Primaries and SecondariesPart 3: Complements, Afterimages, and ChromaPart 4: Problems with the Traditional WheelPart 5: The Munsell SystemPart 6: Cyan, Magenta, and YellowPart 7: The Yurmby Wheel