It can also be a quite a hassle for a newbie who haven't even figured out how to change a theme in GNU/Linux for instance as well :). I've said this before, from the beginning Ubuntu did prove its worth in some aspects but they had chosen the worst color combinations, even for a "decent" look-n-feel and as a result I always felt a bit repulsive towards it.
And whenever I installed a new version one of the "most important" things for me was to get or change the theme to something else.
But there are few GNU/Linux distributions that comes with beautiful colors by default and Fedora is at the top of "my list". Another distribution is the Mint Linux which uses the Green and Black colors quite elegantly. Anyhow, if you use the latest version of the Gnome desktop version 3 who also happened to quite fond of that Greeny Mint Linux theme, then you'd love to hear that there is "related looking" GTK3 theme for Gnome 3 called MintLiner!.
Now remember, by default Gnome 3 uses a Window manager called Mutter (bit similar to Compiz) which is capable of creating all those 3D fancy effects, etc and the plugin that uses Mutter which enables Gnome to create that default, touch screen device optimized interface, is called the "Gnome Shell". The thing is that, you can't use MintLiner in your Gnome Shell interface.
This will only work in your Classic Gnome 3 desktop which can be "forcefully" enabled by the Fallaback mode. So after installing it ... remember it'll only run on the classic Gnome3 desktop, not in the Gnome Shell.
How to install it?
1. First download the archive from here (all credit goes to the creator danodymake) and extract the content.
2. Then copy the extracted folder to "./themes" folder in your "Home" folder or if you want the theme to be available to all the other users that uses that PC/Laptop then copy the content to "/usr/share/themes/".
Now you can apply the theme as usual.
If you want to tweak your Nautilus (file manager)...
The theme has a "css" file which can apply further more "MintLiner-ness" into your Nautilus.
1. To do that first go to the folder "/usr/share/nautilus" and copy the file called "nautilus.css" to your Home folder.
2. Then look for a file with the same name (nautilus.css) in the extracted folder and move it to that above mentioned "/usr/share/nautilus" folder and replace it. Remember you'll have to have root access to do that.
That's it. Now you're done. Enjoy!.