Dithering a Color Image
When there aren't enough colors in a display system to render an image properly, an infinite palette can be created by dithering. Quite often, a 24-bit color image is dithered to 256 colors. The right side is a magnification of the white box on the left.
Text is also dithered. Notice how much softer the word DATABASE is at the top of this example, compared with the undithered word below it. The magnified view shows where lighter blue pixels filled in for the curves. When dithering is performed against the edges of an image, it is called "anti-aliasing."
Learn more about dithering