Redshift is an open-source screen color temperature adjustment tool that automatically adjusts the screen's color temperature based on time to reduce blue light stimulation and help protect vision. It works by adjusting the screen's color temperature according to geographic location and time, transitioning smoothly between daytime high color temperature and nighttime low color temperature. Redshift can be easily installed on Ubuntu through simple commands and can be run through the command line or a configuration file. Users can manually set parameters such as latitude and longitude for precise customization of color temperature.