Yes, I think you're right! This pic of a much older, bigger rat really captures his color better than my photos.
Nevermind, re edit, I can't link the pic. But the Google search confirmed it for me.
My students were asking, so I'll credit you with the correct response! Is this a rare color at all, do you know? I have never seen one quite like him in pet stores. He's a rescue from a feeder bin. (And from a middle school student who couldn't keep him.) It would be interesting to know that a rare coat color came from feeder stock.