I have a shortcut on my KDE desktop that runs this command:

    /usr/bin/redshift -O 3500 -b 0.7

It instantly makes the screen easier to look at, no matter the lighting conditions. I also have a command to revert to normal color:

    /usr/bin/redshift -O 6500 -b 1.0

Curiously, "redshift -O 2700 -b 0.7" is less comfortable than 3500K because it's too yellow. I think what bothers me about screens is heavy saturation in any color.