To invert the entire screen you can use the program
xcalib -invert -alter
xcalib loads 'vcgt'-tag of ICC profiles to the X-server using the XVidMode Extension in order to calibrate your display.
That means it does not depend on compiz being used.
You can install it using
sudo apt-get install xcalib. To make it more convenient assign a keyboard shortcut opening the
There, navigate to shortcuts. Add a custom shortcut by pressing the plus button, add the name and the command. It will be disabled by default, so assign a shortcut by clicking on
Disabled and perform the wanted shortcut, e.g. meta + i
xcalib -invert -alter was launched (mapped to
Pressing it again restores to the normal not inverted screen.