Sony 51'' projection Tv after one hour color chngs to Green

I've come into this problem before, it sounds like the lamp is dieing .. It could also be that a wire connected to the lamp is attached to the wrong post or isn't connected at all.
Depends on how long you've had that lamp installed and use time. If you've been using it for quite some time, 2.5/4 years and never replaced the lamp then it's most likely the lamp that needs to be changed, otherwise if you've had the lamp changed recently, i'd be leaning towards, a wire in the wrong place or not attached at all. Best of luck :)