my cat layed on my g4 powerbook keyboard for awhile and the desktop,any applications,internet pages etc, the screens are like a photo negative ... the colors are reversed and dark. dvds
do the same but the start up screen is normal. They start gray and black and it defaults to 256 colors. when i change to a million colors the color come reversed. i have tried reseting and anything else i could think of
no but results. any insight would be greatly appreciated.....

Quite ironically, I had exactly this problem yesterday!
My girlfriend phoned me in a mad panic, saying that everything worked fine, just the whole display was appearing as a negative.

I had a look on the Apple support site - apparently this is a built-in feature of OSX, part of Universal Access, I presume to help with the visually-impaired (supposedly, negative images can be easier to recognise!!).

The keystorke to get it back is: Control-Option-Command, then press 8 to toggle between the settings.

Here's the Apple link:

All should now be fine!!!