Back in the way old days (System 7?, I don't know it was in 1992) there was a way to invert the LCD Video in preferences. I used to do that on the old PB180 I had way back when for PCB layout. I don't know if the newer stuff has that (Tiger doesn't seem to).
Wait, Just found it. It's in the handicapped acces panel. "Universal Access"
Press Cmd, Opt, Cnt, 8 all at once, that should flip it.
If that doesn't work, I would reset the P ram. Do that by holding down the "P" and "R" keys while rebooting. Hold it for three startup chimes, then let it start normal and with any luck it will be restored to normal.
oooh, this is cool, it inverted all the colors too. Smileys turn blue..
Oh! Even better, you can "Enhance Contrast" and it screws up the video just like a Windblows machine! He he! These Macs and even play dumb
BTW, the Zoom feature is really handy for growing those Windblows Media Slayer shows.
Have fun!