Advance Sprite Palettes

In FF6Tools, when you click on Character Graphics, and go to where you can use that drop down menu on the right to select what color palette to display as, there are 4 weird color palettes there. They are simply named:
Palette 27
Palette 28
Palette 30
Palette 31

Palette 28 is a weird sort of shadow palette that makes whatever sprite is loaded semi see through. The rest are all just this ugly solid puke color. Would it affect anything If I replaced these palettes with other ones? Are they actually used by anything in the game or are they just placeholder palettes that can be overwritten for me to add content?