Question Character back round color icon (Herous of might and magic 5 reference)

So I noticed something interesting thing inside of of games such as HOMAM 5 and song of conquest the icons of units are surround by player units color (unit icons that have color behind them of the same side)
So question how exactly can i replicate this effect?
Should i create a separated icon for each color or make unit icon with empty back round and add something else to it?
I'm stupid so im asking