What is Additive Color?

Legal Definition
Additive color is color created by mixing a number of different light colors, with shades of red, green, and blue being the most common primary colors used in additive color system.

Additive color is in contrast to subtractive color, in which colors are created by subtracting (absorbing) parts of the spectrum of light present in ordinary white light, by means of colored pigments or dyes, such as those in paints, inks, and the three dye layers in typical color photographs on film.

The combination of two of the standard three additive primary colors in equal proportions produces an additive secondary color—cyan, magenta or yellow—which, in the form of dyes or pigments, are the standard primary colors in subtractive color systems. The subtractive system using primaries that are the secondaries of the additive system can be viewed as an alternative approach to reproducing a wide range of colors by controlling the relative amounts of red, green, and blue light that reach the eye.

Computer monitors and televisions are the most common examples of additive color. Examination with a sufficiently powerful magnifying lens will reveal that each pixel in CRT, LCD and most other types of color video displays is composed of red, green and blue sub-pixels, the light from which combines in various proportions to produce all the other colors as well as white and shades of gray. The colored sub-pixels do not overlap on the screen, but when viewed from a normal distance they overlap and blend on the eye's retina, producing the same result as external superimposition.

Another example of additive color can be found in the overlapping projected colored lights often used in theatrical lighting for plays, concerts, circus shows and night clubs.

The full gamut of color available in any additive color system is defined by all the possible combinations of all the possible luminosities of each primary color in that system. In chromaticity space, the gamut is a plane convex polygon with corners at the primaries. For three primaries, it is a triangle.

Results obtained when mixing additive colors are often counterintuitive for people accustomed to the subtractive color system of pigments, dyes, inks and other substances that present color to the eye by reflection rather than emission. For example, in subtractive color systems, green is a combination of yellow and cyan; in additive color, red plus green makes yellow. Additive color is a result of the way the eye detects color, and is not a property of light. There is a vast difference between a pure spectral yellow light, with a wavelength of approximately 580 nm, and a mixture of red and green light. However, both stimulate our eyes in a similar manner, so we do not detect that difference, and both are yellow light to the human eye. (see eye (cytology), color vision.)
-- Wikipedia
Legal Definition
The red, green and blue dyes added to electronic monitors. They are actually seen by the eye not reflected.AKA additive primary colors. Refer to CMYK color model and subtractive colors.