If the enchanted permanent's mana cost is {2}{W}{U}, this Aura's controller adds {C}{C}{W}{U}. If its mana cost is {X}{G}, this Aura's controller adds {G}. If its mana cost is {W/U}{W/U}, this Aura's controller chooses whether to add {W}{W}, {W}{U}, or {U}{U}. The choice may be different each time the ability resolves.