CORRECTION: I set an incorrect horizontal slider length which caused the Caja FM sidepane to be extra wide. I have corrected this now, and the sidepane/treeview should now size properly.
ADDED: Mate Green per request below...
I was toying around with a copy of Ubuntu Mate 18.04 and adapted the Azenis Dark theme (Cinnamon) to work with it. Removed the background that overwhelms the desktop wallpaper. The Metacity had to be completely redone. Themed in the Brisk Menu and the Advanced Mate Menu.
Other than that, it should be very near to the same as the Cinnamon version.
I did this late and in a very cold room. So I did not bother going fancy with the asset placement within folders- but it works all the same. I also did this on an old 32bit computer. IF the metactiy does not work, you can snag the metacity from the following link (just the AzenisBlack.tar.gz file) and swap out the metacity folders:https://www.pling.com/p/1411924/
The Icons are available here:
Extract the .tar.gz to your /usr/share/themes folder or to ~/.themes
Right click your panel and select Background - select custom background image and navigate to /themes/Azenis-black-Mate/gtk-3.0/panel
Open App menu and navigate to Preferences > Appearance. Select Customize and select Azenis Black Mate on the controls, Window border