I am working in front of computer all day long, and looking at the bright screen hurt my eyes. I was relied on the plugin ToggleDocumentColors to give me a grey background and black text with browser. But it does not look good on some web sites and it only works on browser. Then I came across this Redshift program, and it has a SlackBuilds.org script. After installing it with sbopkg, found my latitude and longitude and fire up the program, instantly I could feel the stress of my eyes are reduced.
It may take sometime to get used to it as the color on the screen has a little reddish tone. Unless you are working on graphics or color sensitive work, normal interaction with the web site or application has no problem at all and your eyes got some relief. Since the discovery of this little tool, I have installed it to all my systems.
It has an GUI front end gtk-redshift that comes with the package. It will display an icon on your system tray area, allow you to toggle it by a single click.
Highly recommend this little tool to anyone that need to work in front of computers.