I've been wanting to stay out of this thread, as this issue tends to be pretty contentious. But not a lot of people are posting pictures of their issues, so here's mine.
I've seen a lot of variation in OLED displays, especially on the iPhone X. Some will shift red off axis, others blue and to varying degrees. The native color temp can vary a lot. Some come warmer, which is why we're seeing complain about yellow displays.
My iphone X actually was on the warm end and shifted subtly to red/pink off-axis. But my XS Max has a very warm (yellow) white point and the shift to red is really dramatic compared to my X. You can see the side by side in my picture.
I don't think people in this thread are crazy or making up the issue. It is annoying when white backgrounds turn red when you tilt the phone even a tiny bit. It lowers contrast and reduces readability. There's a pretty big difference in readability of text on my XS Max vs my X.
And while i don't believe serial numbers dictate quality, I will mention that my XS Max serial starts with F2.