Well, I don't recally seeing many details. It was pretty dark those first few scenes. But IIRC, Kevin was supposed to be a science vessel right? (Atleast I think I head something along those lines.) Maybe Robau, bad ass as he was, had a blue uniform because he was a science officer.
As an example, Spock was a part of the command staff, but he wore blue. Scotty was as well, and wore red.
Perhaps something is different in regards to becoming captain, but no one really knows.