Dithering, Shifting and Web-Safe Colors

Using the RRGGBB scheme, we can specify 16,777,216 different colors, but many display cards and programs are limited to 256 colors (chosen from among the 16,777,216). The currently available 256 colors are the current palette, and they are specified in a color lookup table that a program may change at any time.

If you call for the display of a color that is not in the current palette, it will be dithered or shifted. Dithering means mixing dots of different colors to approximate the color you want, and shifting means changing from a color that is not unavailable to one that is close. Dithering and color shifting are okay in a continuous tone photograph, but they look bad in flat color areas like backgrounds, logos and drawings. For those, stick with the Web-safe palette that is common to all Web clients, the 216 colors made up of the RGB values of 00, 33, 66, 99, CC, and FF. You can also safely use these color names:

aqua

00FFFF

black

000000

blue

0000FF

cyan

00FFFF

fuschia

FF00FF

lime

00FF00

magenta

FF00FF

red

FF0000

white

FFFFFF

yellow

FFFF00

Here is a table showing the Web-safe colors.

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