<P> Arranging spectral colors in a circle to predict admixture of light stems from work by Sir Isaac Newton . Newton's calculation of the resulting color involves three steps: First, mark on the color circle the constituent colors according to their relative weight . Second, find the barycenter of these differently weighted colors . Third, interpret the radial distance (from the center of the circle to the barycenter) as the saturation of the color, and the azimuthal position on the circle as the hue of the color . Thus, Newton's color circle is a predecessor of the modern, horseshoe - shaped CIE color diagram . </P> <P> The psychophysical theory behind the color circle dates to the early color triangle of Thomas Young, whose work was later extended by James Clerk Maxwell and Hermann von Helmholtz . Young postulated that the eye contains receptors that respond to three different primary sensations, or spectra of light . As Maxwell showed, 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 . </P> <P> There is no straight - line relationship between colors mixed in pigment, which vary from medium to medium . With a psychophysical color circle, however, the resulting hue of any mixture of two colored light sources can be determined simply by the relative brightness and wavelength of the two lights . A similar calculation cannot be performed with two paints . As such, a painter's color wheel is indicative rather than predictive, being used to compare existing colors rather than calculate exact colors of mixtures . Because of differences relating to the medium, different color wheels can be created according to the type of paint or other medium used, and many artists make their own individual color wheels . These often contain only blocks of color rather than the gradation between tones that is characteristic of the color circle . </P> <P> A number of interactive color wheel applications are available both on the Internet and as desktop applications . These programs are used by artists and designers for picking colors for a design . </P>

In the visible spectrum what color comes between orange and green