<P> A color wheel or colour circle is an abstract illustrative organization of color hues around a circle, which shows the relationships between primary colors, secondary colors, tertiary colors etc . </P> <P> 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 . For instance, some reserve the term color wheel for mechanical rotating devices, such as color tops or filter wheels . Others classify various color wheels as color disc, color chart, and color scale varieties . </P> <P> As an illustrative model, artists typically use red, yellow, and blue primaries (RYB color model) arranged at three equally spaced points around their color wheel . Printers and others who use modern subtractive color methods and terminology use magenta, yellow, and cyan as subtractive primaries . Intermediate and interior points of color wheels and circles represent color mixtures . In a paint or subtractive color wheel, the "center of gravity" is usually (but not always) black, representing all colors of light being absorbed; in a color circle, on the other hand, the center is white or gray, indicating a mixture of different wavelengths of light (all wavelengths, or two complementary colors, for example). </P> <P> 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). The divisions of Newton's circle are of unequal size, being based on the intervals of a Dorian musical scale . Most later color circles include the purples, however, between red and violet, and have equal - sized hue divisions . 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 . </P>

Who invented the color wheel and in what year