Earlier I wrote about manually installing GTK themes in Gnome Shell. This can be done relatively easier using the Gnome Tweak Tool.
Download a GTK theme. I will use the Adwance theme.
The downloaded theme needs to be placed in the /usr/share/themes/ folder. Press Alt + F2 and run
Navigate to File System > usr > share > themes
Extract your downloaded theme and place the extracted folder in the themes folder you navigated to.
Open the Gnome Tweak Tool.
Under Interface, choose your theme from the GTK Theme dropdown box.
To change the title bar theme, go to Windows, and choose your theme from the Current theme dropdown box.
For it to take effect, restart Gnome Shell. To do so, press Alt + F2 and run “r”.>