Web Design in a Nutshell, 3rd Edition

Color Palette

Animated GIFs, like static GIF files, use a list of up to 256 colors that can be used in the image. They can have multiple palettes (one for each frame) or one global palette. The palette choice affects how well the images appear on the inevitable variety of systems and monitor setups.

One problem with using multiple, frame-specific palettes is that they can cause a flashing effect on some early versions of Navigator (it cannot load the frames and their respective palettes in sync). In any case, multiple palettes dramatically increase file size. It is recommended you use one global palette for the whole animation. GIFMation and Ulead GIF Animator allow you to create a customized global palette. In fact, any image editor can be used to create a global palette. Just place all images to be used in one document, and then index the document. The resulting palette will be a global palette for the entire animation.