Before Sugar interface went all Web 2.0 and YUI'y in 2010, I was taming the hundreds of classes and code inconsistencies to create a coherent and clean interface. Actually tens of interfaces because Sugar had multiple personalities - below are some skins I designed and implemented for SugarCRM, version 5.5 circa 2008.
I had designed and updated several CSS skins for this application, which look completely different yet follow 2 navigation schemas and share the same code base for the main window.
Unfortunately, there was little control over spacing or charts or placement of most elements. Other challenges included inconsistencies in code for different views (list view vs. edit view vs. home vs. calendar, etc.) and tables upon tables upon tables...
All of the themes allowed to increase font size and some had up to 6 color variations.