Redshift is an open-source screen color temperature adjustment tool that automatically adjusts the screen's color temperature according to the time, reducing blue light stimulation to the eyes and helping users protect their vision. It works based on the geographic location and time, smoothly transitioning the screen color temperature between daytime and nighttime. Redshift can be easily installed on Ubuntu using a simple terminal command. Users can run Redshift through the command line or a configuration file to customize settings such as latitude, longitude, and color temperature.