I thought M2 was learning his colors and I was a bit surprised. But, now I see that he just likes to say his version of blue. He can say red too, so he often alternates at random.
He is starting to be a joker though. I like how he tries to say yellow - he can't get his mouth to work like he wants - so I was encouraging him to say yellow banana. He got a big kick out of saying "boo" (blue) and giggling every time I asked.