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. For instance, some reserve pantone color wheel pdf term color wheel for mechanical rotating devices, such as color tops or filter wheels.

The typical artists’ paint or pigment color wheel includes the blue, red, and yellow primary colors. The corresponding secondary colors are green, orange, and violet or purple. Other color wheels, however, are based on the four opponent colors, and may have four or eight main colors. A wedge-shaped gap represents colors that have no unique spectral frequency. These extra-spectral colors, the purples, form from additive mixture of colors from the ends of the spectrum. In normal human vision, wavelengths of between about 400 nm and 700 nm are represented by this incomplete circle, with the longer wavelengths equating to the red end of the spectrum.

Complement colors are located directly opposite each other on this wheel. For example: the reason that the Wimbledon tennis tournament uses purple on the Wimbledon official logo is that purple is located almost opposite of green on the color wheel. Purple against green provides good contrast. The color circle is used for, among other purposes, illustrating additive color mixture. Combining two colored lights from different parts of the spectrum may produce a third color that appears like a light from another part of the spectrum, even though dissimilar wavelengths are involved. This type of color matching is known as metameric matching. Objects may be viewed under a variety of different lighting conditions.

The human visual system is able to adapt to these differences by chromatic adaptation. This aspect of the visual system is relatively easy to mislead, and optical illusions relating to color are therefore a common phenomenon. The color circle is a useful tool for examining these illusions. 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. 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. 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.

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. The HSL and HSV color spaces are simple geometric transformations of the RGB cube into cylindrical form. Color schemes are logical combinations of colors on the color wheel.

Tetradic color palettes use four colors, a pair of complementary color pairs. For example, one could use yellow, purple, red, and green. Tetrad colors can be found by putting a square or rectangle on the color wheel. In color theory, a color scheme is the choice of colors used in design for a range of media. For example, the use of a white background with black text is an example of a common default color scheme in web design. Color schemes are used to create style and appeal.

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