You can ask any modder if they could make the palette index for the sprites, but if you're going to keep modding, you'll have to learn how to do it yourself. When I first noticed this problem myself, I used copies of ready-made sprites of other things, and just edited those (because they have the palette index ready), until I learned how to apply the palette on my computer.
Try copying the zombie sprite files and editing them with the palette colors. I did that for some time. It works though.
The error with the body armor is probably the fact that the game won't read the Coalition.rte before reading Base.rte, so it doesn't find the armor piece. (this is, of course, if you're modifying the Base.rte's zombies) You could try making a separate .rte file, and take a look what a basic .rte consist of (most importantly an index.ini). This could very well be the start of your first working mod.
I hope this helps!
