Currently, when you click/activate one of your units, you will see a green circle around the unit. Equally, when you select an enemy unit, a red circle will show around it. Other than for red-green blind people, that's good as it is in my opinion.
However, when you play cooperatively with other players, it would be nice if their units, when selected by you, would have a different color circle around them than the enemy. Currently, this circle will be red, but I find this non-intuitive. I suggest to change the color of the circle drawn around selected friendly units to yellow.