Well, you've 7 OW palletes, right?
Pallete 4 is grass and pallete 6 is earth, you can leave these how they are.
Pallete 0-3 are unuseable, because some strange things will happen on your OW during the events.
Pallete 5 and 7 are used for a few small things, like the water, shadows and stuff.
All those small stuff can easily fit in one pallete, so you've to copy those colors to one pallete:
See, I've left 4 and 6 the same (well I've changed 6 to a volcano pallete, but you can leave it the same)
Then I've copied all the important colors from 7 to 5. (see picture)
And after that, you can change pallete 7 into whatever you want (desert in my picture)
However, there are a few problems you should keep in mind:
- You have to replace ALL the water (which normally uses pallete 7) with pallete 5-water.
- You're blue switch pallace will look a bit funky (depending on your pallete 7)
- Same for the shadows (for under bridges)