Took my M1 11” into Best Buy today to compare to the M4. There were two of the 11” and one 13”. Color was a little warmer/yellower on the M4s. Not alarmingly so, but enough to make me unsure of how well it would fit into my photo editing workflow. I came away thinking that it was probably close enough (my work doesn’t require absolutely perfect accuracy), but at the same time it was another point in favor of hanging on to my M1 for now.
I should note, however, that this was in bright store lighting with the display brightness turned all the way up… could look better (or worse) in my more typical dimmer light and midway screen brightness, I’m not sure if color temp of these screens changes depending on that setting.