gnome-shell-extension-redshift software package provides redshift extension for GNOME Shell, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gnome-shell-extension-redshift
gnome-shell-extension-redshift is installed in your system.
Make ensure the gnome-shell-extension-redshift package were installed using the commands given below,
$ sudo dpkg-query -l | grep gnome-shell-extension-redshift*
You will get with gnome-shell-extension-redshift package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | GNOME |
| Package | gnome-shell-extension-redshift |
| Version | 3.20.1-2 |
| Description | redshift extension for GNOME Shell |
| Sub Section | gnome |