Install gtk-theme-switch by entering the following commands in the terminal:
sudo apt update sudo apt install gtk-theme-switch
Description:
GTK+ theme switching utility
Utilities to easily switch GTK+ themes that can be run from the console, and has an optional GUI dock and theme preview. It can install themes downloaded from gtk.themes.org as well straight from the tarball.
Homepage: http://gna.org/projects/gtk-theme-switch/
Version: 2.1.0-5build1
Section: universe/x11