I am!!! I have styled a Menubar without any problems, as the identifiers are easily found googling around, not the rootpane.
The only inline style that I still have laying around in my code is just this one, and I want to pass it to my css file, which is already added to my form!
Even the B4J documentation has no reference on the identifiers to include in a css file for known views.
as far as I'm aware, using # means setting the views ID, which I want to avoid, just because that would target that particular view, and not the type of view,
but its a start.
it worked in your example, but not in mine... using the JavaObject method didn't help.
there is something fishy going on with this css, both your approach with JavaObject, as well as mine with the stylesheets attribule, do style the menubar, but not the root pane.