I own a Mitsubishi Diamond WD-57831 57" DLP display which I have loved immensely for the last year and a half, and the grey scale has always been spot dead on.
Recently, I have noticed that it is showing a slight green tint, mostly in low light situations. I have tweaked the "Perfect Color" and "Prefect Tint", but it hasn't solved it, but has helped.
It now looks a bit better with the white levels (Contrast) about 85%, where it was at 50%.
Anyone experience this? I feel it may be the lamp, with approx 2000 hrs on it.