It's just an image. They have a background image for the gray/teal -
http://www.orbforum.com/styles/oxyge...background.png - and then the image for the logo is just in a div inside of that div with the background -
http://www.orbforum.com/styles/oxyge...go_spotify.png
Basically like this:
<div id="header_background">// this div has the background image
<div id="inner">
<div id="left">
<img src="logo_image.png" />
etc...
</div>