The RYB primary colors became the foundation of 18th century theories of color vision as the fundamental sensory qualities blended in the perception of all physical colors and equally in the physical mixture of pigments or dyes. These theories were enhanced by 18th-century investigations of a variety of purely psychological color effects, in particular the contrast between “complementary” or opposing hues produced by color afterimages and in the contrasting shadows in colored light. These ideas and many personal color observations were summarized in two founding documents in color theory: the Theory of Colors (1810) by the German poet and government minister Johann Wolfgang von Goethe, and The Law of Simultaneous Color Contrast (1839) by the French industrial chemist Michel-Eugène Chevreul.
Additive color mixing—red and green combining to make yellow, for example, or blue and yellow producing white—runs counter to the commonsense observation that, for example, yellow paint plus cyan paint makes green paint. The wavelengths of light that reach the eye are often selected via these more intuitive subtractive processes: for example, cyan paint appears to our eye as cyan because it absorbs red wavelengths, and a yellow paint appears yellow because it absorbs blue wavelengths. When white light falls on a combination of cyan and yellow, then, both red and blue are absorbed, and green is reflected to the eye.
There are two types of color mixing: Additive and Subtractive. In both cases there are three primary colors, three secondary colors (colors made from 2 of the three primary colors in equal amounts), and one tertiary color made from all three primary colors.
Additive mixing of colors generally involves mixing colors of light. In additive mixing of colors there are three primary colors: red, green, and blue. In the absence of color or, when no colors are showing, the result is black. If all three primary colors are showing, the result is white. When red and green combine, the result is yellow. When red and blue combine, the result is magenta. When blue and green combine, the result is cyan. Additive mixing is used in television and computer monitors to produce a wide range of colors using only three primary colors.
Subtractive mixing is done by selectively removing certain colors, for instance with optical filters. The three primary colors in subtractive mixing are yellow, magenta, and cyan. In subtractive mixing of color, the absence of color is white and the presence of all three primary colors is black. In subtractive mixing of colors, the secondary colors are the same as the primary colors from additive mixing, and vice versa. Subtractive mixing is used to create a variety of colors when printing on paper by combining a small number of ink colors, and also when painting. The mixing of pigments does not produce perfect subtractive color mixing because some light from the subtracted color is still being reflected. This results in a darker and desaturated color compared to the color that would be achieved with ideal filters.
A subtractive colour model explains the mixing of a limited set of dyes, inks, paint pigments or natural colorants to create a wider range of colors, each the result of partially or completely subtracting (that is, absorbing) some wavelengths of light and not others. The color that a surface displays depends on which parts of the visible spectrum are not absorbed and therefore remain visible.
Subtractive color systems start with light, presumably white light. Colored inks, paints, or filters between the viewer and the light source or reflective surface subtract wavelengths from the light, giving it color. If the incident light is other than white, our visual mechanisms are able to compensate well, but not perfectly, often giving a flawed impression of the “true” color of the surface.
Conversely, additive color systems start with darkness. Light sources of various wavelengths are added in various proportions to produce a range of colors. The component lights may be inherently colored or simply white light that has passed through suitable subtractive color filters; their combination is an additive one in either case. Usually, three primary colors are combined to stimulate humans’ trichromaticcolor vision, sensed by the three types of cone cells in the eye, giving an apparently full range.
RYB (Red, Yellow, Blue) is the formerly standard set of subtractive primary colors used for mixing pigments. It is used in art and art education, particularly in painting. It predated modern scientificcolor theory.
Red, yellow, and blue are the primary colors of the standard color “wheel”. The secondary colors, violet (or purple), orange, and green (VOG) make up another triad, formed by mixing equal amounts of red and blue, red and yellow, and blue and yellow, respectively.
In late 19th and early to mid-20th century commercial printing, use of the traditional RYB terminology persisted even though the more versatile CMY (Cyan, Magenta, Yellow) triad had been adopted, with the cyan sometimes referred to as “process blue” and the magenta as “process red”.