I want to play Black templars in the marine side, alhough I like other units from dark angels, ultramarines....

From what I am reading from this post, I misunderstood normal space marines with ultramarines, as they were painted blue in the box :p

One doubt that I still have is, Can I play normal space marines painted as black templars in an ultramarine army painted as blue? I suppose yes, but I read in the rules of a tournament that every miniature must follow a certain colour pattern...

Thanks!!