Behind blue eyes

I have picked a male blue merle collie puppy out of a litter; they are currently five and half weeks old, and he has two bright blue eyes. Here is a photo of him:

I already have a blue merle dog who is two years old, and he has one blue and one brown eye. I have never seen a blue merle with two blue eyes; will they stay blue or will they go brown or wall eyed?

Sarah, Wigan