Redshift update the color temperature of your screen according to the moment of the day.
During the day your screen have a « normal » color (5700 K) and when the night comes the temperature go down progressively.
So during the night your screen will have a red tint.
This will help your eyes and also reduce the blue light effect.( the blue light enable the production of melatonine by your body, that prevent you to sleep.)
To install and configure on Arch
If you have an issue with geolocalisation check your parameter in gnome settings.
And also in geoclue :
sudo vim /etc/geoclue/geoclue.conf
You may need to add:
To finish create and modify the config file for redshift :
; Global settings for redshift
; Set the day and night screen temperatures
; Enable/Disable a smooth transition between day and night
; 0 will cause a direct change from day to night screen temperature.
; 1 will gradually increase or decrease the screen temperature.
; Set the screen brightness. Default is 1.0.
; It is also possible to use different settings for day and night
; since version 1.8.
; Set the screen gamma (for all colors, or each color channel
; This can also be set individually for day and night since
; version 1.10.
; Set the location-provider: 'geoclue', 'geoclue2', 'manual'
; type 'redshift -l list' to see possible values.
; The location provider settings are in a different section.
; Set the adjustment-method: 'randr', 'vidmode'
; type 'redshift -m list' to see all possible values.
; 'randr' is the preferred method, 'vidmode' is an older API.
; but works in some cases when 'randr' does not.
; The adjustment method settings are in a different section.
; Configuration of the location-provider:
; type 'redshift -l PROVIDER:help' to see the settings.
; ex: 'redshift -l manual:help'
; Keep in mind that longitudes west of Greenwich (e.g. the Americas)
; are negative numbers.
; Configuration of the adjustment-method
; type 'redshift -m METHOD:help' to see the settings.
; ex: 'redshift -m randr:help'
; In this example, randr is configured to adjust screen 1.
; Note that the numbering starts from 0, so this is actually the
; second screen. If this option is not specified, Redshift will try
; to adjust _all_ screens.