Here is “Aubergine.” Another simple Numix based GTK3 theme that is easy on the eyes as well as pleasant to look at. It is GTK 3.20 compatible, as well as Unity etc.. I find the colours match very well. However, the archive includes instructions on how to edit the colours yourself if you wish to tweak them.
To install for all users, extract the theme and copy its parent folder to the following folder (you will need root privileges):
To install just for yourself, extract the theme and copy its parent folder to the following folder (you will need to be able to view hidden files and folders):
The theme screenshots are taken on Xubuntu Xenial.
Version .02 Changes 6 months ago
The only thing that changed is the instructions on how to set up LibreOffice to seamlessly fit into the theme. The spreadsheet "grid Lines" were the same color as the Document Background. This has been fixed via the new instructions.
Thanks to the fellow who pointed this out via EMAIL instead of simply grading the theme down. It was appreciated!