Phillips HDTV Turned Green

The Philliips 60" rear projection HDTV I've had for about 3 years
turned green for a short time last night, and then flashed back and
forth between green and normal. So I turned it off and went to sleep. 

Iit was back to normal this morning when I watched it for about 1/2
hr., but I suspect that the problem is going to come back sooner or
later. I was just wondering if I'm looking at a costly CRT
replacement, as I suspect. Or could  it be a minor, hopefully, less
expensive problem?

Thanks in advance or any help anyone can give me on this.