Artists use the RYB color model with the primary colors of blue, red and yellow. The primary colors are arranged at equidistant points along the color wheel. The secondary colors, green, orange and violet, are formed by combining nearest sets of primary colors. Likewise, the tertiary colors, blue-green, blue-violet, red-orange, red-violet, yellow-green, and yellow-orange, are made by combining a primary color with it's nearest secondary colors. The arrangement of these colors around a circle corresponds with the wavelengths of light and are ordered in accordance with Isaac Newton's original color circle.
The RYB primary colors were the basis of the 18th century theories of color. These theories along with personal observations of color were detailed in the two founding documents of color theory: The Theory of Colors (1810) by Johann Wolfgang von Goethe, and The Law of Simultaneous Color Contrast (1839) by Michel-Eugene Chevreul.