Aloha - I followed the instructions of the accepted answer here
However, it doesn't work for me on 16.04. Not sure if its that creating the gtk.css file method doesn't work on 16.04 or if I am just having an issue.
I use a non default theme, if that makes any difference. I have the base16 themes in a folder within .config and preloaded into terminal with 'source' command.
In the image you can see I have 2 open tabs, plus I show the output of my gtk.css file
