For me, the 13 pm is a warmer/pinkish color during setup, I did notice the os seems to balance it out a bit with software.Well, the 13PM's screen looks yellower and less vibrant than the X's. This is with the auto-brightness and true tone turned off.
One interesting thing, when setting up a new phone, the outgoing phone always looks whiter with more contrast, I remember thinking last year that my 11 max screen looked better than 12 pm. So maybe give it some time.