My second display monitor- a 20-inch Apple monitor - connected to my Macbook Pro has gone negative. I've tried the control-option-command-8 route, but that only makes the second monitor normal, and turns my Macbook Pro monitor negative.
Rebooting doesn't help, nor does disconnecting and reconnecting the monitor. Can't seem to find an answer on the Apple forums. Any help greatly appreciated.
Problem solved. For anyone else with this problem, using an older Mac monitor that uses a box into which the monitor cable and power supply are plugged, unplug the cables from the box then replug. That's the fix.