primary colors.........

Primary colors:

Primary colors are sets of colors that can be combined to make a useful range of colors. For human applications, three are often used; for additive combination of colors, as in overlapping projected lights or in CRT displays, the primary colors normally used are red, green, and blue. For subtractive combination of colors, as in mixing of pigments or dyes, such as in printing, the primaries normally used are magenta, cyan, and yellow. Any choice of primary colors is essentially arbitrary; for example, an early color photographic process, auto chrome, typically used orange, green, and violet primaries.

Additive combination:

Almost all visible colors can be obtained by the additive color mixing of three colors that are in widely spaced regions of the visible spectrum. If the three colors of light can be mixed to produce white, they are called primary colors and the standard additive primary colors are red, green and blue. Media that combine emitted lights to create the sensation of a range of colors are using the additive color system. Typically, the primary colors used are red, green, and blue.

Television and other computer and video displays are a common example of the use of additive primaries and the RGB color model. The exact colors chosen for the primaries are a technological compromise between the available phosphors (including considerations such as cost and power usage) and the need for large color triangle to allow a large gamut of colors.

SUBTRACTIVE COMBINATION:

Two colors that produce white when added together are called complementary. The color complementary to a primary color is called a secondary color. The complementary or secondary colors for red, green and blue are cyan, magenta and yellow respectively. These three colors are often referred to as the subtractive primary colors. When the three are combined in subtractive color mixing, they produce black.