The newly announced Bluebird theme for XFCE and Gnome has a nice clean look. Using this metacity theme and the Zuki Blues theme, I went all Blue for May. Included are Chromium and Firefox personas also in blue. Below are my results and a link where to get the themes...
The Zuki Blues theme can be found here:
http://lassekongo83.deviantart.com/art/Zuki-Blues-175190463?q=&qo=
The Bluebird metacity theme can be found here:
http://gnome-look.org/content/show.php/Bluebird+metacity?content=140011
Chrome Bluebird theme:
https://chrome.google.com/webstore/detail/hedddjdackneeciinimepakidindpgdd