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A color can be described in terms of three varying characteristics, called the HSB color 
model: 

• Hue—tint (the qualitative aspect of a color—red, green, or orange)

• Saturation—the purity of the color

• Brightness—relative position between white and black 

While the CIE chromaticity diagram (plate 2) conveys hue and saturation, a three-
dimensional color model is required to add the brightness component (plate 3).

Many computer applications include dialog boxes in which you choose colors by 
manipulating hue, saturation, and brightness. For example, Photoshop uses a square 
Color Picker (plate 4) which can be reconfigured according to your preference.

Color devices used in desktop publishing and printing simulate the range of visible 
colors using a set of primary colors that are combined to create other colors. There are 
two methods for creating a range of colors from a set of primary colors. Computer 
monitors and scanners are based on the additive color model. Printing technologies, 
including Fierys and offset presses, are based on the subtractive color model.

Color devices that use the additive color model make a range of colors by combining 
varying amounts of red, green, and blue light. These colors are called the additive 
primaries (plate 5). White is created by adding the maximum amount of red, green, 
and blue light available. Black occurs wherever all three colors are absent. Grays are 
created by adding equal amounts of all three color together. Combining varying 
amounts of any two of the additive primaries creates a third, saturated hue.

A familiar device that is based on this color model is the computer monitor (plate 6). 
Monitors have red, green, and blue phosphors that emit varying amounts of light to 
display a given color. Scanners create digital representations of colors by measuring 
their red, green, and blue components through colored filters.