Hello Linux Geeksters. As you may know, Numix is a flat theme that combines well dark and light elements. The Numix theme is available in two versions, the Numix GTK theme, which is compatible with Gnome, Unity, XFCE and Openbox, and the Numix KDE theme, compatible with KDE.
In this article I will show you how to install either Numix GTK or Numix KDE, depending on your desktop environment, on Ubuntu 14.04 Trusty Tahr, Ubuntu 13.10 Saucy Salamander, Ubuntu 13.04 Raring Ringtail, Ubuntu 12.10 Quantal Quetzal, Ubuntu 12.04 Precise Pangolin, Linux Mint 16 Petra, Linux Mint 15 Olivia, Linux Mint 14 Nadia, Linux Mint 13 Maya and Elementary OS 0.2 Luna.
Because it is available via PPA, installing Numix GTK or Numix KDE is easy. All you have to do is add the ppa to your system, update the local repository index and install one of the following packages: numix-gtk-theme or numix-kde-theme. Like this:
$ sudo add-apt-repository ppa:numix/ppa
$ sudo apt-get update
$ sudo apt-get install numix-gtk-theme #for GTK systems
$ sudo apt-get install numix-kde-theme #for KDE systems