This is a module for sStats, a data display framework.
The sStats API may be found on the sStats page: http://www.wowinterface.com/downloads/fileinfo.php?id=14814
Currently, when changing the prefix/suffix text colors in the sStats config window, the durability frame's text does not update right away. This has to do with the text only updating when the event fires for your character's durability updates. You can either be patient or reload your UI (/reload).