Battles.
Right now, battles are melee units on front line (up to 20 in a line), any other melee units lined up behind them to take the place(s) of any getting killed. Ranged units and mages behind any lines of melee units. AI determines where the units are placed in lines. If the unit commander(s) are melee units, they are on the front line.
Units earn experience for fighting battles (or sitting with a 'training' commander.
Map colors look ok to me. Not sure what you may be expecting.
Monsters ain't my favorites...they kill my units
I found a Beholder once...it was an army unto itself. I ran away.
To me, it's a cross between COE2 and Dom3. I really like the way it plays. Testing Dom 3 was a lot of work. COE3 is a lot of work too, but I seem to be enjoying it much more. I'm not the guru that Gandalf and Edi are, so they can give a lot better details than I can.