Hi Milka,
I can't give you a diagnosis, but a very similar thing happened to a Samsung flat screen I had. In my case the splotches were blue, but it sounds very familiar. Here's a picture from mine (ignore the white dots on the left side - those are reflections from the Christmas tree).
[image|2713372]
The spots started out as a single spot that got bigger over time, and others started appearing as well. Fortunately for me, mine was still under warranty so I got a replacement. The old one is now in the garage at my son's house, used for workout videos. It still works and the spots eventually stopped growing, but they're still there.
The upshot is that the Costco Concierge service determined the TV wasn't repairable and authorized a replacement, so I'm afraid that doesn't bode well for yours, assuming it's the same problem.
Hopefully someone with more specific expertise in the area of television repair can add their considered opinion.
If you were to add a photo of your TV showing the problem, I'm sure it would help with diagnosing the problem.