Okay, some progress. As you can see I found out what the bg_color value controls in Linux gtkrc:
I still have tweak the color scheme. When I finish and publish it If you use Linux you will get 3 files; eclipse.gtkrc, ecrun(bash script), and e4_default_gtk.css file. And its simply move the files to the right places and no messing around with plugins.
This is the tweaking that the adt-bundle should have received as than it shows some polish. I say that because this past summer Google recruiters were attempting to get me to go through the application process for a developer advocate position. This is the type of stuff we care about among other things.
Contrary to popular misconception you do not need to create a plugin to do a theme, at least the minimum e4 css one. You will not have to create a plugin until you start fully customizing editors.