Redshift

Redshift is an automatic color temperature adjustment to help reduce monitor eye strain induced by working in low-light conditions. Depending on the location (longitude and latitude) of the user's computer system, Redshift will change the color of the screen from the default bluish color to a orange/reddish color during evening hours, and then back again to bluish tint during daylight hours.

Emerge
After setting necessary USE flags, install Redshift:

Files
A configuration file can be created in each users home directory at

In order for Redshift to start, it will require longitude and latitude information inside the configuration file.

Add correct location information into the configuration file. Lat/Lon values can be found searching for the closest city or region at Wikipedia or with a map service such as OpenStreetMap.

When using OpenScreetMap, simply search for the location. When it appears on the map tiles click the button (should be near the top left). The center of the displayed tiles will be the exact Lat/Lon location. The Lat value is the second number from the end displayed in the URL. The Lon value is the last number on the end.