Huumph. I thought I answered already, but anyway, and this is quote from the starter guide:
:: Dorm System ::
As you have noticed your rank is red, Slifer Red. We have 3 dorms: Slifer Red, Ra Yellow and Obelisk Blue. For us, you are valuable as much as you show us in here, what you are outside, it does not concern us. This means, you start as Slifer Red and work your way up to Obelisk Blue. There is also Abandoned Dark Dorm which is highest. This dorm is reserved only for the best, the ones with many achievements here in DA. Currently, we are working on a new, improved testing system for ranking up to a higher dorm. Until then, only way to rank up is to participate in tournaments and events which give ranking up as a reward.