elpa-zenburn-theme software package provides low contrast color theme for Emacs, 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 elpa-zenburn-theme
elpa-zenburn-theme is installed in your system.
Make ensure the elpa-zenburn-theme package were installed using the commands given below,
$ sudo dpkg-query -l | grep elpa-zenburn-theme *
You will get with elpa-zenburn-theme package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Lisp |
| Package | elpa-zenburn-theme |
| Version | 2.4-1 |
| Description | low contrast color theme for Emacs |
| Sub Section | Lisp |