2 BlueHeavenHero
Take a look at the work of comrade Zobr as an option. If he duplicates the link, it would be great because I don’t remember where I saw it here.
If briefly, then it is desirable not to overload the background with details. Choose a general color so that it contrasts with the units but looks logical for the faction. Plus, the unit should be brighter than the background - either dim the colors of the background or illuminate the unit. In general, if you look without peering closely, the accent color spot should be on the unit, and not behind it or to the side/front.
here is my mod, but I think my backgrounds are quite overloaded)
the problem here is in the color scheme; the units and their buildings have the same color! A light paladin on a light wall and a dark green vampire on a dark green X.
It’s easier in vanilla; only the gremlin blends in with the sand....