I think what you are calling "pastelish" on his back is what we call blushing. Blushing comes in varying degrees on normals. For example - extreme blushing on one of my normals:



Second observation - I see two things that I'm concerned with - a) you haven't quarantined your new baby from your established adult and b) it appears that you are housing them together when they should always be housed individually and only out together AFTER a 90 day quarantine.