Hi,
There is a link on this forum where I actually wrote a tutorial how to copy that theme design.
The page you see in the image is actually a normal webpage. If you click on the Moodle link in the little white menu top left you will see this page...which IS the Frontpage of my Moodle site.
In that Moodle site I colored the background for the side blocks, but it is easy enough to make them transparent.
You can do that with any theme. Most of the styleing on a page is done with CSS (Cascading Style Sheets), in much the same way that the webdesigners styled the Zen Garden Project If you have never seen the individual designs on that site then it's time you did as it will give you inspiration to learn all about how important CSS is in webdesign.
THE MARVELOUS thing about CSS is that one HTML page can be designed in a thousand other ways as you will see HERE. So to answer your question it's all done using CSS.
Here is the link to the tutorial I was talking about earlier...
http://moodle.org/mod/forum/discuss.php?d=199850#p871590
If you want some help just say so...I am always willing to help people learn new tricks!
Cheers
Mary