Natural Color System (NCS)

The Natural Color System (NCS) is a proprietary perceptual color model published by the Scandinavian Colour Institute (Skandinaviska Färginstitutet AB) of Stockholm, Sweden. It is based on the color opponency description of color vision. The system is usually used for matching colors (using printed reference cards), rather than mixing colors.

The NCS is based on the six elementary color percepts of human vision - the psychological primaries - as described by color opponency - white, black, red, yellow, green, and blue - which are difficult to define perceptually in terms of others. All the other perceptual colors are composite perceptions that can be defined in terms of those six (for example, turquoise looks like "blue green", orange like "a color that is both reddish and yellowish," and brown looks like "a very dark orange," that is, like a mixture of red, yellow and black). This all means the appearance of a color can be readily predicted from its NCS notation, whereas its notation in systems such as RGB often looks unintuitive (for example, yellow does not look like "a reddish-greenish color" at all, even though the yellow on an RGB monitor is obtained by mixing red and green lights).

Colors in the NCS are defined by three values, specifying the amount of blackness (darkness), chromaticity (saturation), and a percentage value between two of the colors red, yellow, green or blue (hue). The blackness and the chromaticity together add up to less than or equal to 100% - their remainder from 100%, if any, gives the amount of whiteness. The complete NCS color notations can also be tagged with a letter giving the version of the NCS color standard that was used to specify the color.

The NCS is represented in 19 countries and is the reference norm for color designation in Sweden (since 1979), Norway (since 1984) and Spain (since 1994). It is also one of the standards used by the International Colour Authority, a leading publisher of color trend forecasts for the interior design and textile markets.