Inspired by Redshift, Blueshift adjusts the colour temperature of your monitor according to brightness outside to reduce eye strain and make it easier to fall asleep when going to bed. It can also be used to increase the colour temperature and make the monitor bluer, this helps you focus on your work.
Blueshift is not user friendly and it is not meant to be, although its user friendlyness is increasing. Blueshift does offer limited use of command line options to apply settings, but it is really meant for you to have configuration files (written in Python 3) where all the policies are implemented, Blueshift is only meant to provide the mechanism for modifying the colour curves. More Info »
Blueshift provides no safe guards from making your screen unreadable (this feature [the lack of a feature] is used in the sleepmode example) or otherwise miscoloured; and Blueshift will never, officially, be tested on any proprietary operating system. It may however add theoretical support and be tested on Free Software clones (for example ReactOS). Blueshift is fully extensible so it is possible to make extensions that make it usable under unsupported systems, the base code is written in Python 3 without calls to any system dependent functions (with exception for fallbacks.) This is not necessarily true for configuration script examples and optional features.
If Blueshift does not work for you for any of these reasons, you should take a look at Redshift. The main reason for using Blueshift over Redshift is to add adjustments that they implemented in Redshift or using very customised behaviour, such as the example configurations scripts sleepmode, xmobar and xmonad.