Many color systems have been developed throughout history, including those developed by Tobias Mayer (1758), Johann Goethe (1810), and M.E Chevreul (1864). (For more information about the history of color systems, click here).
The color wheel taught to most people today is the twelve hue color circle developed by Johannes Itten. This color wheel is based on a triadic mixture of pigments with red, yellow, and blue as the primary triad. All hues are formed from mixtures of equal or unequal amounts of primaries. Equal mixtures of two primaries result in the secondary hues and form the triad of green, orange, and violet. In this color wheel, six intermediate hues are created from equal mixtures of primary and secondary colors and form two more triads.
When mixing pigments or dyes, color mixture is described as subtractive. When white light (or sunlight) hits a surface, light wavelengths are absorbed. We perceive only the color that is reflected from the surface. Pigments or dyes subtract (absorb) particular wavelengths of white light, while the remaining wavelengths are reflected, forming the colors that we see. If no light is absorbed, we perceive white; if almost all of the light energy is absorbed, we perceive black.
In theory, equal mixtures of subtractive primaries should result in black pigment, however, when mixing red, blue, and yellow primaries together, the resulting mixture is more likely to be dark gray, brown, or greenish. The Itten color wheel works well as a chart, but due to the variety and inconsistencies of actual pigments and dyes, it is imperfect as a practical guide for the mixture of tube colors. Pigments in paint vary greatly in opacity and undertones, and it is difficult to create pure secondary and tertiary hues from primary mixtures. Mixed colors tend to lose their saturation, therefore, if you want intense color, purchasing pure tube colors is best.
Additive color mixtures pertain to the properties of light and were first explained by Isaac Newton. We form all colors of light by adding combinations of colors from the spectrum. When all the separate color wavelengths of light are mixed together, the result is white light. Likewise, if white light is separated into distinct wavelengths of color using a prism or water particles in the air, for example, the result is a spectrum or rainbow of colors.
The primary colors of light are red, green, and blue (RGB), and are used to create the colors on your television screen (or computer monitor). For more information about color used in television and video, click here.
Equal mixtures of additive primaries result in white light. When blue and green light are blended they form "cyan", the complement of Red. When red and blue light are blended, they form "magenta", the complement of Green. When green and red light are blended, they form "yellow", the complement of Blue.
Before the widespread use of digital ink jet and laser printers, commercial four-color offset lithography printing presses used inks based on a color wheel comprised of Cyan, Magenta, and Yellow as the primaries (with black). This subtractive color wheel accurately matched printing colors to the corresponding (complementary color) dyes used in color film negatives. The foundation of modern film-based color photography was based on this set of primaries and secondaries. In color films, such as Kodacolor, the dyes used in the film negatives were complementary to the colors printed on the paper positive. (The orange cast of a color negative was used to correct deficiences in the color dyes which did not filter light uniformly). The complementary colors of cyan, magenta, and yellow are red, green, and blue (RGB). The primary and secondary colors in the CMY subtractive color wheel and the RGB additive color wheel are the same.
Today, most printing is done using inkjet printers that are interfaced with computers and RGB displays. Photoshop, as well as other digital imaging software are based on RGB color that outputs on CMYK printers. CMYK inks are used because of their direct relationship to the RGB colors of the computer monitor. CMYK inks are referred to as "process" colors, a reference to the traditional four-color printing process. The "K" stands for black, because color plates were registered or "keyed" to the key line of the black plate.
Black is printed in combination with CMY, because equal combinations of CMY inks do not produce a pure black (because of variations in pigments and transparencies). Black ink also creates cleaner text, and text is of course, frequently used in printing. In addition, it is far cheaper to use black ink than to combine CMY to create black. Printmakers in the fine arts using the traditional processes of intaglio, silkscreen, relief, and lithography also use process Cyan (turquoise), process Magenta (rose), and process Yellow as primaries, because these three particular primaries create a full range of fairly pure secondary and intermediate colors.
Although the CMY secondaries are red, green, and blue, these color mixtures in pigment do not have the same intensity as their additive counterparts. Transparent inks, however, allow light to be reflected from the paper's surface through the inks, creating more luminosity than opaque color.