This script implements a reading mode/grayscale mode in i3 window manager and other window managers using compton.
The level of desaturation is 95%, so there is still some color present, but it's desaturated to a very large degree.
This has no effect on your wallpaper: I recommend setting a black wallpaper using hsetroot.
In grayscale mode, backend is always glx.
compton-grayscale-reading-mode is a wrapper around compton. Any command line arguments are passed along to compton.
Any running compton instances are killed, therefore this script can be used to switch grayscale mode on and off.
Enable grayscale mode
MODE=grayscale compton.sh
Disable grayscale mode
MODE=normal compton.sh