I can't be positive, but I think you're describing something that happens on my Hitachi 43" as well. I suspect it's internal reflections in the lens housing - like a lens flare in reverse. I see it mostly (or really only) in high contrast scenes like the opening of Fifth Element when the bright blue arc of earth swings into view against the black starfield background. As soon as the bright part of the picture comes into view, the dark areas of the screen picks up a touch of the blue-ish cast with a stronger arc that moves opposite the apparent source.
Every once in a great while it bugs me, but not really enough to cause me to lose sleep. (BTW: Brightness:51, Contrast:36, but I *have* pulled the front panel and tweaked the RGB knobs, so my numbers may not bear any relation to yours.)