I have had my Roku Ultra for less than a week. I've used other Roku products (Stick+, Premiere) and had a similar issue with my Premiere.
We were watching Netflix and everything was looking fine. At the end of our program we went to the home screen and everything started to have a green tint. All menus. All channels/apps (including Netflix), everything has a green tint.
I checked for firmware updates (no new updates found). Changed resolution sizes (no help), and did a factory reset (didn't work).
I moved the Roku Ultra to a different TV and it was back to normal. I checked the TV by itself and it does not have a green tint (Now watching Netflix through the TV App).
I plug the Roku to the TV again - Green Tint. I try a different HDMI port -Green Tint. I try different HDMI Cable - Green Tint.
In the past I unplugged the Premiere for about 30 seconds and it worked, but that happened only once.