UPDATE: ingolemo has updated v0.3 of his theme, incorporating my improvements :-) -- http://gnome-look.org/content/show.php/Ubuntu+Sun?content=116344. Please use his theme, which is under active development.
* * *
This theme combines the Sunny metacity theme (http://gnome-look.org/content/show.php/Sunny?content=116529) with the Human theme (the latter is a dependency). Specific improvements to ingolemo´s v0.2 metacity theme include: (1) fixed all edges and corner highlights; (2) replaced the up-down window-button animations with subtle button highlights on hover and click; and (3) added visible buttons to all unfocused windows.
To change the default color scheme, just click on System -> Preferences -> Appearance -> Colors, and change the Selected Items Background color.