Ahem, how do you mean 'what set'? You do not expect that we describe each color for each country right?
For me personally the most disturbing in Titanium was almost same color for Japan and USSR, so USSR may keep it's color and Japan can take yellow, while China bright and dark orange (Nat and Com China). Actually, IIRC in Gold version colors were just fine.
As for marshes, plains, hills, mountains, towns, jungles, deserts - Mod34 has nice convenient colors but not perfect, while most other mods often have color of marshes like place how I imagine paradise - green with much yellow and such. Plus often you can make mistake between marches and jungles and even think that marshes are plains actually or forests.
Looking at mod34 as reference point, I would put deserts slightly more yellow, marshes with slightly more blue in that green, plains with greenish borders, jungles slightly darker in green and towns in all mods I would put in red. Because towns are most important strategic points they need to have distinctive and somewhat disturbing color like red, but preferably dark red cause we do not wish to send warning to our eyes every time we look upon terrain map. Forests, mountains and hills are OK there.
English is not my native language so I described my wishes according to knowledge of words of basic colors.
P.S. After I wrote all of this, I saw that you did not ask for terrain colors just for country colors LOL.

o