Orange is produced by mixing red and yellow.
Green is produced by mixing blue and yellow.
Violet is produced by mixing red and blue.
These primary and binary colors are thought of as though they were arranged in a circle.
Divide the circumference of a circle in six equal parts. Draw three diameters through the points found. Begin at the top with yellow. One-sixth of the distance to the left, we place orange, at the next diameter’s end place red. At the bottom of the circle opposite yellow is violet. Passing upward toward the right blue is opposite orange, and continuing upward, green is opposite red. The colors at opposite ends of the three diameters are called complements.
Yellow is the complement of violet and violet of yellow.
Orange is the complement of blue and blue of orange.
Red is the complement of green and green of red.
The outside of the circle in the cut represents the full strength of the pure color. The addition of different amounts of white and black is indicated by the inner circles, the center standing for pure white or pure black. The circle may be subdivided to suggest many gradations from the full color through the tints to white and by the addition of black through the shades to black. This system of gradation is a help in determining the contrast of tints, but is more useful in helping to determine related harmonies up and down the scale from black to the pure color and then through the tints to white.
Red, with one part of white added, would be indicated by the second circle. Its complement would be the green found on the second circle, which has an equal amount of white mixed with it, producing a tint. The same arrangement holds true with regard to black. Each circle represents also one portion of black added to the standard color, producing a shade. There is an almost indefinite number of these tints and shades, depending upon their location within the color circle.