making generic pallets

[Mando]

Ok, so I have stumbled upon some fairly hidden pallets that have been done already but atm they are in .png format (I can convert them to .bmp easy thats not a prob.)

Question I have is, how do I compile these different color versions of the same sprites into a single .bmp file so they can be used as generics?

Cause then it would be cool to use to replace a lot of the ugly looking normal FFT sprites.