A color wheel is a circular diagram depicting the various colors of the visible spectrum and their relations to one another.
Basic color wheels start by placing the three primary colors (red, yellow and blue) at equal points around the edge of the circle, then filling in the intermediary spaces with the colors created by mixing them (orange, green and purple).
Color wheels can be very simple, containing only six colors, or extremely complex, containing the entire range of colors that can be produced by mixing the basic hues.
Some color wheels incorporate black or white as well. Generally, either color will form the center of the circle, and all the colors around the edge will fill in the whole circle, becoming gradually lighter or darker as they approach the center.
Color wheels may be built upon sets of colors other than the standard primaries. The most common variants are the primary colors of light (red, green and blue) and the primary colors of pigment (cyan, magenta and yellow).