Reducing Color Depth

As can you see, if you remove some colors, the GIF doesn't change so much. But it get smaller:

256 colors original GIF (size: size="2">53 Kbytes size="2">)	128 colors GIF (size: size="2">44 Kbytes size="2">)


64 colors GIF (size: size="2">34 Kbytes size="2">)	32 colors GIF (size: size="2">26 Kbytes size="2">)