Chosen Solution
I have had my thunderbolt display for a while and no issues until one day it seems to click, and the green appeared. After about 10-15mins it disappears and the screen is back to normal. The green is all over with what looks like some image persistence at the sides. I have stripped the display back but could see anything obvious then wasn’t sure what to look for. I gave everything a clean with a blower, a long shot but no joy… Any advice welcome.
Try cleaning the connections with a qtip and alcohol and a soft brush, there might be corrosion just from the humidity in the air. Update (05/21/2020) If you open it up it should have a connection where you can change the screen.it should be internal. I use Rubbing alcohol as high of a percent of alcohol.
