In game, you have red/green. In spectator mode, you have blue/yellow. I can't see the difference between creeps when playing (nor can I in Dota), but in spectator mode I can see better. Since these 4 colors already exists - while it can be better - it would be amazing if we ourselves could just pick friendly and enemy color from these 4 options for starters. Ideally, we could just pick colors ourselves from a normal colorpicker like you would see in art/design software. Some games have already implemented this, like Elder Scrolls Online based on community feedback and it works great.