It seems the confirmed new Ultras are Rosso, Bull and um, Lube. Rosso is the masculine word for red in Italian. Bull should perhaps be Blu in Italian, because there isn't the long sound at "bu" as would be in ブール, the more accurate spelling of Bull. The "u" is also a short one, whereas in the English "Blue" it would be long. This is like how Bullton can be translated as Bluton. So I guess they're going with colour names. As for Lube, I have no idea but I have heard that it is an approximation of Louve which means female wolf.  Edit: Apparently Bull IS in fact spelt buru in Japanese, with the short "bu". So I guess there is a chance that he is called Bull.