Updated 2/8/2016: new package names, edited for clarity.
sudo apt-get install redshift-gtk
On Arch, the package is just “redshift.”
First thing we need to do is find your latitude and longitude. To do this, go to http://itouchmap.com/latlong.html and enter your general location. For this guide I’ll be using NYC, which shows up as 40.714353,-74.005973.
Open a terminal and run:
redshift-gtk -l 40.71:-74.00 -t 6500:3700
for your latitude:longitude, of course.
Press ctrl+c to cancel when you’re done.
If you ran this at night you should see the display change colors. If you ran it during the day and nothing happens, that’s exactly how it should work. The -t switch defines a daytime temperature (6500k) followed by a nighttime temperature (3700k). At 6500k your monitor color shouldn’t change, while at 3700k your display should change to a red/orange color.
Now just add the command to your application autostart menu and you’re all set. (ex: Click menu -> type “startup” and add the command there). And reboot or logout/login.
Source: man redshift