This is a write up to fully explain color tables, how they work and how to use them. Tis about time we made an effort to eliminate some of the confusion. This is a work in progress as my time is always at a premium.
If I remember well, a well organized color table makes the files smaller. For exemple, an image using a palette with only 6 colors close to the beginning will be smaller than a image using a palette with 6 colors elsewhere or close to the end, because to have those 6 colors, you will have 249 empty spots.
Well yes of course it has to be organized right to get the full benefit, but that's superfluous information for a basic tutorial.
Aside, most imaging programs do that anyway. Annoyingly so in fact - if you aren't paying attention to what you're doing, Photoshop will merrily reorganize color tables to make them optimal whether you like it or not.