I think Apple probably have serious issue with iPhone 12 production. I believe all the iPhone 12 with yellow tone display may have defect oled panel; I visited Costco store today, and they have iPhone 12 mini, iPhone 12 pro max, and iPhone 12 on display. All have yellow tone except one iPhone 12, which has the correct color display. As shown in the picture here, on the left is last year iPhone 11 Pro max; in the middle is the new iPhone 12 (with correct color display - color filter is turn off); on the right is iPhone 12 mini with yellow tone display. The iPhone 12 in the middle has highest brightness (I set brightness on all the phones to max); in the picture iPhone 12's font/letter look washed-out because of the way I took the picture. In make eyes, the color on the iPhone 12 looks pretty good.
My iPhone 12 pro had a yellow display, and I took it to Apple store on Sunday; Apple Genius Bar ran a test on it and told me that the display was defected. I decided to return the phone instead of exchange for the new one. I will wait until Apple fix the issue before I buy the iPhone 12 again.