Typical for the non-amoled screens I've owned: N4,IPS; N5,IPS; N5X,LED; N7,LCD; N7.2,LCD; and N9,LCD. I didn't own the N6, but have the GNexus and the 6P which have versions of amoled. If your screen appears more yellow than what my pic shows (or, better, as suggested, store comparison), it does need to be replaced.
The OLED is a samsung display (not super saturated for sure) and maybe should be better than it appears on the phones--yours and mine. I've read that a disadvantage of OLED (vs AMOLED) is variation of color balance. I don't believe the yellow factor has shown up on xda--yet. The "brightness" (or lack of) factor has been discussed. I know when I turned my display all the way up, I was able to see it clearly in the very bright sunlight while using sunglasses. I do have to keep the display at 50% of the slide even inside house/car.