probably as a circle
color will represent nation, the letter will represent race.
perhaps it could be a circle drawn in another, one color representing nation, the other race, and then the letter represents if the unit is militia, heavy infantry, ect.
or it could just be one circle with two letters
there will also be the thin black outline, it helps set the shape out and can be used to show when the shape is being selected.
in time the game could perhaps move to figures, or even sprites.