Okay So we have purchased a 42in Curtis Plasma screen and when we turn the tv off it keeps like a low blue?

I also recently purchased a curtis. And it does the same thing. The salesman at the store said that he called the company and they told him it was normal. They told him that the tv keeps the plasma a certain temperature and that if the room were warmer it wouldn't glow. I have yet to test this theory but may fire up the wood stove in the room one of these days to see if that is true. If it is correct my guess is that it has something to do with how fast the tv turns on.