Install gtk2-engines-nodoka by entering the following commands in the terminal:
sudo apt update sudo apt install gtk2-engines-nodoka
Description:
Nodoka theme engine for GTK+ 2.x
The engine behind the new default theme for Fedora, Nodoka is inspired by such themes engines as Clearlooks and Murrine. It features smooth, subtle gradients and rounded widgets. . Also included are a variety of GTK+ themes using the Nodoka engine.
Homepage: https://fedorahosted.org/nodoka/wiki
Version: 0.7.2-0ubuntu3
Section: universe/gnome