After 1 hour and lots of maneuvers, loading both vanilla and Magna Terra, I get this beautiful thing:
It's... homogeneous and... uniform and... yellow...
Well, the terrain is tricky... it seems I can't work with colormap_hires easily.
First I can't get colormap_hires working in the mod folder.
Second I tried "my" colormap_hires with europe re-scaled and yellow in the other places. Well, everything went yellow.
Third, to achieve this picture I had to create a whole yellow world with the altered colormap_hires, then eliminating all vanilla provinces texture cache, then using the vanilla colormap_hires and loading vanilla Rome to calculate the "old" textures for vanilla provinces. Then running Magna Terra and voilá, vanilla map + yellow world.
In short: not good.
*Hides Terra Universalis mod in my signature*
EDIT: Lolz @ the timing of this discussion, 3.2 released, I need to update Terra Universalis now