Media playback is one of the core experiences of Android TV, so when the latest version of Android, 6.0 Marshmallow, was sent to Nexus Players with a significant bug related to color reproduction, people were understandably upset. Specifically, it seems like colors are appearing washed out. Blacks will end up looking gray and other colors do not look correct either when media is being played.
The issue was posted in the Android bug tracker in early October. As some commenters pointed out, this only affects videos, not the OS or other apps. Even then, it only seems to affect hardware decoded videos. This issue seems to have affected the Nexus 6P and 5X phones on Marshmallow as well.
As you can tell in this comparison, submitted by Obm…@gmail.com on the issue, the colors look much worse on Marshmallow.
Somebody from Google did respond and recently confirmed the issue exists and that they’re quickly working on a fix. For the Nexus phones, a fix is already complete and will be part of an upcoming update. This update will likely contain many more emoji as well as having a bunch of bug fixes like this. It’s likely that the bug affected the Nexus Player will be part of this round of updates as well.