Screen shows blue instead of black pixels; external display is normal

My 15” 2010 MBPro screen suddenly looks very strange. It has a blue tint, in fact I ran a color pattern test and everything that should show up as black shows up as blue. Red looks very similar to magenta. But my external screen hooked up to mini-display port looks perfectly normal, black patterns show up perfectly as do all other colors. Tilting the display back and forth has no affect either.

Is there any way to tell if this problem is due to wiring, LCD panel, or backlight problem?

NOTE: I’ve installed gfxCardStatus, and switching between integrated & discrete graphics makes no difference. Also, I have iStat Menus installed, and “Left Heat Pipe/Fin Pipe Proximity” just shows a dash, no temps. No idea if that was always the case, just noticed it now trying to troubleshoot this screen problem.