Redshift

Redshift + Xorg + KDE

If you're running KDE and Xorg, you'll likely need to use Redshift to tint your screen at night. "Redshift Control" is a KDE widget that gives you a nice GUI to configure Redshift (found by searching the "Get new widgets" interface).

I also found (in this video) what might be the command line way to install both redshift and the plasma widget:

sudo apt install redshift plasma-applet-redshift-control

Although elsewhere I've seen an additional program recommended:

sudo apt-get install plasma-widget-redshift plasma-applet-redshift-control

Configuring Redshift in Plasma

First, I'd recommend moving the widget to the task bar. Then, to configure it, simply right-click the widget and click configure. Hit "Locate" to automatically locate your position. Then for temperature 6500 for Day and 3250 for Night seems to work well.

GTK (GNOME)

For gtk-based desktop environments like GNOME, you're probably going to want to run sudo apt-get install redshift redshift-gtk