COLORS

Colour or color[1] is a property of light as seen by people. In Commonwealth English, it is spelled “colour” (notice the U), while in American English it is “color”

"Primary colours" can be mixed to make other colours. Red, yellow, and blue are the three traditional primary colours. The primary colours for television screens and computer monitors are red, green and blue. Printers and paints use magenta, yellow, and cyan as their primary colours; they may also use black. Sometimes this set of colours is simply called red, yellow, and blue.

People who can not see colours or have a distorted sense of colour are called colour blind. Most colour blind people are male.

Colours are sometimes added to food. Food colouring is used to colour food, but some foods have natural colourings, like beta carotene.

When something has no colour, it is transparent. An example is air.

The science of color is sometimes called chromatics, colorimetry, or simply color science.

A translucent material is not the same as a colourless material because it can still have a colour, like stained glass.

colour, also spelled color, the aspect of any object that may be described in terms of hue, lightness, and saturation. In physics, colour is associated specifically with electromagnetic radiation of a certain range of wavelengths visible to the human eye. Radiation of such wavelengths constitutes that portion of the electromagnetic spectrum known as the visible spectrum—i.e., light.

Vision is obviously involved in the perception of colour. A person can see in dim light, however, without being able to distinguish colours. Only when more light is present do colours appear. Light of some critical intensity, therefore, is also necessary for colour perception. Finally, the manner in which the brain responds to visual stimuli must also be considered. Even under identical conditions, the same object may appear red to one observer and orange to another. Clearly, the perception of colour depends on vision, light, and individual interpretation, and an understanding of colour involves physics, physiology, and psychology.

An object appears coloured because of the way it interacts with light. The analysis of this interaction and the factors that determine it are the concerns of the physics of colour. The physiology of colour involves the eye’s and the brain’s responses to light and the sensory data they produce. The psychology of colour is invoked when the mind processes visual data, compares it with information stored in memory, and interprets it as colour.

Aristotle viewed colour to be the product of a mixture of white and black, and this was the prevailing belief until 1666, when Isaac Newton’s prism experiments provided the scientific basis for the understanding of colour. Newton showed that a prism could break up white light into a range of colours, which he called the spectrum(see figure), and that the recombination of these spectral colours re-created the white light. Although he recognized that the spectrum was continuous, Newton used the seven colour names red, orange, yellow, green, blue, indigo, and violet for segments of the spectrum by analogy with the seven notes of the musical scale.

A colour can, however, be precisely specified by its hue, saturation, and brightness—three attributes sufficient to distinguish it from all other possible perceived colours. The hue is that aspect of colour usually associated with terms such as red, orange, yellow, and so forth. Saturation (also known as chroma or tone) refers to relative purity. When a pure, vivid, strong shade of red is mixed with a variable amount of white, weaker or paler reds are produced, each having the same hue but a different saturation. These paler colours are called unsaturated colours. Finally, light of any given combination of hue and saturation can have a variable brightness (also called intensity or value), which depends on the total amount of light energy present.

Colours of the spectrum are called chromatic colours; there are also nonchromatic colours such as the browns, magentas, and pinks. The term achromatic colours is sometimes applied to the black-gray-white sequence. According to some estimates, the eye can distinguish some 10 million colours, all of which derive from two types of light mixture: additive and subtractive. As the names imply, additive mixture involves the addition of spectral components, and subtractive mixture concerns the subtraction or absorption of parts of the spectrum.