Colors, Fonts, and
Keyboards
135
Chapter 9 9
Color
9.1 RGB and Other Color Systems
Almost all modern color computer displays display colors by combining varying
amount of red, green, and blue (RGB) light. These three colors stimulate the eye??™s
color receptors and approximate the sensation of viewing various colors; for example,
orange light with a wavelength of about 600 nm cannot be produced by a computer
screen, but emitting a modest amount of green light, a large amount of red
light, and no blue light will provoke a sensation in the eyes of most viewers that will
be indistinguishable from the sensation of viewing orange light.
Throughout X, color is spelled without a u, reflecting the American
origins of the system. However, for those of us raised in Canada, the
U.K., or any of the other commonwealth countries, that u is a hard
habit to break, and it can lead to all sorts of mischief including syntax
errors??”so check your u at the door!
Since the perceived colors are created by the addition of three different wavelengths
of light, this RGB color is considered to be an additive color system. The red, green,
and blue colors used are called additive primaries.
Computer printers, on the other hand, use a subtractive color system.
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