Here is the MXML file for the header controller. You can find my changes by searching for "LJA", hopefully I initialed all of the spots I modified.
To get the widget skin to match, I modified the PNG files on lines 90, 91, 92 in the \Skins\CustomWidgetTemplateSkin.mxml file (opened PNG, and applied a new gradient, keeping same image size). These are located in Assets/Images/Custom.
Hope this is useful.