I recently went through something like this. One day, all of a sudden I had problems with my cable. Basically, everything that was dark colored was now green and everything else was a light purple. After experimenting, I found out it was only my cable seeing this problem. I tried connecting it by component instead of HDMI and the problems weren't there. Then I tried swapping my cable box for another one and replacing the HDMI cable and it still had the same problems.
I went through three different attempts to fix the problem through replacing boards inside the TV. Finally, after the third one didn't work, they let me replace the TV (I had gotten the extended warranty) so I got a bigger, better TV to replace it without spending anything extra.
