FlatSquare - it's a simple theme, performed in 16 colors from Google recommendations Material Design. Ideal for interfaces, placed in a flat square style.

Installing:
Instructions for Debian and Kubuntu (probably works for other distros too)
Extract FlatSquare.tar.gz
Copy folders to /home/.kde/share/apps/aurorae/themes
Then go to System Settings>Workspace appearance and choose you favourite theme.

Author:
modos189