James Clerk Maxwell showed that all hues, but not all colors, can be created from three primary colors such as red, green, and blue, if they are mixed in the right proportions. Thomas Young postulated that the eye contains receptors that respond to three different primary sensations, or spectra of light. Color scientists and psychologists often use the additive primaries, red, green, and blue and often refer to their arrangement around a circle as a color circle as opposed to a color wheel. Most later color circles include the purples, however, between red and violet, and have equal-sized hue divisions. The divisions of Newton's circle are of unequal size, being based on the intervals of a Dorian musical scale. The original color circle of Isaac Newton showed only the spectral hues and was provided to illustrate a rule for the color of mixtures of lights, that these could be approximately predicted from the center of gravity of the numbers of 'rays' of each spectral color present (represented in his diagram by small circles). In his book Opticks, Isaac Newton presented a color circle to illustrate the relations between these colors. Others classify various color wheels as color disc, color chart, and color scale varieties. For instance, some reserve the term color wheel for mechanical rotating devices, such as color tops, filter wheels or the Newton disc. Some sources use the terms color wheel and color circle interchangeably however, one term or the other may be more prevalent in certain fields or certain versions as mentioned above. A color wheel or color circle is an abstract illustrative organization of color hues around a circle, which shows the relationships between primary colors, secondary colors, tertiary colors etc.

Primary colors color wheel