In an RTS game where the units are viewed from the top so that they appear relatively small on the screen:
What would be the best game design?
Colour the units per team, for example: enemy is always red, player's units is always blue
Colour the units per ability, for example: the "destroyer" is always red, the "collector" is always green, the "interceptor" is always blue, etc. This will only work with the assumption that the teams would never have the same units and that there are only a small number of different types of units per game.
A combination of 1 & 2 so that the enemy is always represented by warm colours and the friendly units with cold colours. Different unit types are represented by different shades of a colour.
If I choose (1) I am concerned that the player might get confused which unit is which and for example try to attack with the wrong unit type.
If I choose (2) I am concerned that the player might be overwhelmed with too many colours and will not be able to easily tell the enemy from the friendly units.
If I choose (3) I am concerned that it might confuse the players: e.g. say the "destroyer" was light red (enemy) in one game and the next game the player switches sides so that the "destroyer" turns light blue (friendly), the player might not recognize the unit as a "destroyer".