Adobe Illustrator CS4 - Manual (Page 101)

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Chapter 4: Color
Applying colors to artwork is a common Adobe Illustrator task, and one that requires some knowledge of color models
and color modes. When applying color to artwork, keep in mind the final medium in which the artwork will be
published, so that you can use the correct color model and color definitions. Experimenting and applying color is easy
using the feature-rich Swatches panel, Color Guide panel, and Edit Colors/Recolor Artwork dialog box in Illustrator.
About color
About colors in digital graphics
We use color models to describe the colors we see and work with in digital graphics. Each color model, such as RGB,
CMYK, or HSB, represents a different method for describing and classifying color. Color models use numeric values
to represent the visible spectrum of color. A color space is a variant of a color model and has a specific gamut (range)
of colors. For example, within the RGB color model are a number of color spaces: Adobe® RGB, sRGB, and Apple®
RGB. While each of these color spaces defines color using the same three axes (R, G, and
B), their gamuts are different.
When you work with the colors in a graphic, you are actually adjusting numerical values in the file. It’s easy to think
of a number as a color, but these numerical values are not absolute colors in themselves—they only have a color
meaning within the color space of the device that is producing the color.
Because each device has its own color space, it can reproduce colors only in its gamut. When an image moves from one
device to another, image colors may change because each device interprets the RGB or CMYK values according to its
own color space. For example, it is impossible for all the colors viewed on a monitor to be identically matched in a print
from a desktop printer. A printer operates in a CMYK color space, and a monitor operates in an RGB color space. Their
gamuts are different. Some colors produced by inks cannot be displayed on a monitor, and some colors that can be
displayed on a monitor cannot be reproduced using inks on paper.
Even though it is impossible to perfectly match all colors on different devices, you can use color management to ensure
that most colors are the same or similar enough so they appear consistent.
See also
“ About color management in Adobe applications ” on page 132
“ Synchronize color settings across Adobe applications ” on page 134
RGB
A large percentage of the visible spectrum can be represented by mixing red, green, and blue (RGB) colored light in
various proportions and intensities. Where the colors overlap, they create cyan, magenta, and yellow.
RGB colors are called additive colors because you create white by adding R, G, and B together—that is, all light is
reflected back to the eye. Additive colors are used for lighting, television, and computer monitors. Your monitor, for
example, creates color by emitting light through red, green, and blue phosphors.