floatbg software package provides slowly modify the color of the X root window, 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 floatbg
floatbg is installed in your system.
Make ensure the floatbg package were installed using the commands given below,
$ sudo dpkg-query -l | grep floatbg *
You will get with floatbg package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | X Window System software |
| Package | floatbg |
| Version | 1.0-28+b1 [armhf], 1.0-28 [amd |
| Description | slowly modify the color of the X root window |
| Sub Section | x11 |