One of the more interesting*features of the 6-inch, 2560×1440 AMOLED screen is that, on the lowest brightness, it turns pink. We're going to call this a feature, and not a bug, since the screen can do normal-color low brightness at about the same level*as the Note 4 (2*cd/m2). While Samsung just stopped at that point with its*AMOLED screen, Motorola takes things a step further and goes for the absolute lowest brightness without regard for color accuracy. This pink mode allows the Nexus 6 to hit (0.9*cd/m2)—one of the darkest displays we've ever seen. The pinkness doesn't really bother us when we're just trying to get stuff done in the dark. Our primary concern is not being blinded.
Because of the way brightness works in Lollipop, you're only able to get this pink mode in a dark environment. "Adaptive Brightness" is meant to be on all the time. It works like automatic brightness, but there is still a slider you can adjust.
When you're not in the dark, the colors on the screen are fine. It's still an AMOLED display, though, so you're still dealing with oversaturated colors.