File: white thing.gif (1 KB, 64x64)

1 KB GIF

1. Open up GIMP (or any other program that can edit GIFs)
2. Open the colormap/palette window under Windows Dockable Dialogs
3. Change colors
4. Save and export as GIF- be sure to check "Loop forever" and "One frame per layer"

You can convert it from indexed color to direct RGB by using Image Mode if you want to add any wacky effects- just remember to use the color dropper tool to add any new colors to the palette after you convert it back to indexed (256 max).