Backdrops/Wallpapers look wrong in OS 3.1

[Yasu]

I have gotten myself a MiST and am currently trying to pimp my workbench so it reminds me of how my A1200 used to look like around 1997. It came with an HDF with pre-installed MWB and I've installed NewIcons over it. Problem is that I want to use a backdrop/wallpaper that has 21 colors in it, but while I can get it to show the correct colors when I use a 256 color screen, anything below that (128, 64 or 32 colors) will show the backdrop with the wrong colors.

What can I do to fix this?

[Yasu]

Thanks. I tried using Fullpalette before but I wasn't able to get the color I wanted. But now I tried again, and after upping to 64 colors (giving me the right palette), locking the colors and then reducing to 32 colors again it worked! Thanks