I don't think there is an option to change the color of enemy effects, but there should be. For example, when I would try using Dark Convergence as a melee build, I couldn't tell if the purple ball is mine or an enemy's. Even if I don't use it, I can't tell if it is a friendly effect or not. So, to be safe, I have to do my defensive anyway. Would be nice if there was some way to differentiate between them. If there already is, great; please let me know what it is.