I got my iPhone 12 Pro 256gb-Graphite a few days ago, serial starting in DNPDN. Comparing with my XS, my iPad Pro, and the Macbook I have at home, there was definitely a green tint to the screen. There's a lot of speculation in this thread and other internet forums and I was going back and forth about exchanging the 12P, so I decided to collect some data.
I used Duet Display on the 'Pixel Perfect' setting with my i1Display Studio/DisplayCal via the 'Verification' tab, after setting the spectral correction to RGB OLED family (Sony PVM-2541, Samsung Galaxy S7, Lenovo LEN 4140). I set both phones as close to 250 nits as I could.
The attached images show the measurement results. The basic color temperature measurements are ~6500K for the XS and ~6400K for the iPhone 12P, but temperature doesn't tell the whole story. The RGB gray values show that my XS has some extra red content, but my 12P has higher green levels. My XS is lot a less uniform, which could be a result of the differential aging of OLED pixels (blue ages faster than green, which ages faster than red).
Interestingly enough, this matches with
this Youtuber's measurements.
Anandtech found their 12P had high red levels, so I think the story that Apple has relaxed tolerances for this initial batch, given worldwide supply constraints, is fairly credible.
I think I'll play the screen lottery once, and if the exchanged one isn't satisfactory look for an AppleCare repair in the spring.