Help! Screen colors black & white and inverted

Title pretty much says what is wrong. I got a little angry at a beachball; and must've hit some keyboard shortcut I dont know.
False alarm; nevermind. I found that I mustve hit a shortcut that turned on black & white contrast. Found it in the Universal pane of Sys Prefs. Ok; back to color & non-inverted now. hmm... that inverted was kind of neat though... :D