Since Ubuntu MATE haven't any green colored close buttons for it's windows, I made some. So, here my work and I think you guys may like it!
Just download, extract and, with sudo, put then on:
/usr/share/themes/Ambiant-MATE/metacity-1.
The orange ones will be replaced with new green ones!
This is how it will looks like after installed:
Download:
https://uucloud.ddns.net/index.php/s/fJjAt47MXcrHj3t