Before Redshit I was using f.lux  which seems to be broken in Ubuntu’s Unity. I searched for an alternative & found positive reviews about Redshift, which is inspired by f.lux.
By default, redshift fetches your approximate location using the internet (geoclue method) & uses it. if you prefer to manually set it, check the help. And if you, like me, prefer it to use a preset location &/or other configuration (without having to do it every time you run your system), create a text file named redshift.config under your ~/.config/ directory. You can do this from the terminal:
In this file, copy & edit the content below:
;This is a configuration file for the screen color temperature adjuster Redshift.
;Copy this file to your ~/.config/ directory for redshift to use.
;All lines starting with a semicolon areignored (e.g, adjustment-method).
;To change your location, edit the lat & lon numbers. If these two lines are set to be ignored, redshift will fetch your location using the internet.
; Global settings
; The location provider and adjustment method settings are in their own sections.
Make sure to edit the numbers in the last two lines to correspond to your location, before saving & exiting the editor.
This way, every time redshift runs, it uses this configuration file. If you want it to automatically run on startup, add it to your Startup Applications (command: gtk-redshift for the gui & redshift for the cli).
Unlike f.lux, redshift only has a “toggle” option in the gui. The toggle toggles redshift on/off in case you need to. Other preferences are edited from within the configuration file or from the terminal.
I’d like to thank the the code author, Jon Lund Steffensen, for making this tool; It is, to my knowledge, the only alternative to f.lux for Linux.
That’s basically it for now. May your eyes stress less while you work!