I mentioned it to other threads myself, i agree completely, check the "magic the gathering" system how much advanced it is, if they would take atleast some elements from it, it would make things a lot more interesting, here s the page with the five colors http://www.wizards.com/Magic/Multiverse/Colors.aspx of course you cannot be all colors, because some colors oppose the others, black magic and white magic cannot go together for instance, but you have many variations of multiple combinations, like earth, water and black magic or fire, earth and white magic
This is kind of off-topic, but you are wrong, back when I played MAgic (like three years ago) a friend of mine had a deck with all the colours, and it was very good. In fact there are cards that need all the colours. You are also wrong about the black and white thing. I had an incredibly good white and black deck, and they sell many black and white pre - made decks. And also, this is not Magic: The Gathering, this is TES. I am not against borrowing from other games, but I don't think they should take ideas from a card game
Anyway, I don't like the idea of being limited to spells based on class, they should be limited based on skill. If I have a low Conjuration skill and a high Destruction skill, I shouldn't be able to summon the most powerful creature.