Application #1: Making the screen red to preserve night vision
(from here: http://ubuntuforums.org/showpost.php?p=6803029&postcount=4 - by sanskaras)
The trick is basically to switch off green and blue entirely. The proposed solution is modifying these two channels with the -green and -blue command line paramters. I've realized that these quite powerful commands are not documented in the README currently, hence here's the description:
-green GREENGAMMA GREENBRIGHTNESS GREENCONTRASTWith these switches and the -alter command it is possible to modify the existing color behavior.
-blue BLUEGAMMA BLUEBRIGHTNESS BLUECONTRAST
-red REDGAMMA REDBRIGHTNESS REDCONTRAST
Hence, the following is, according to the link, a possible setting for disabling green and blue.
xcalib -green .1 0 1 -alter
xcalib -blue .1 0 1 -alter
When all is over or the screen became unreadable, you can always revert back to normal: