Well, thats a difficult question to answer because im not sure what you mean, well im not sure what the white bar is in the first place.
My form is a borderlayout, inside "contentpane" I have NORTH, CENTRE, SOUTH, but im presuming that is not relevant. So looking at component inspector I have what you would expect Toolbar contains StatusBar, and a container with 2 buttons with TitleCommand uuid.
Now I want the text to be white and the background to be whatever the rest of NORTH is. So I tried styling StatusBar and TitleCommand, but none of my changes have any affect, I delierately used bright colours so it would be easy to notice.
I wonder if its related to having the side menu ?? Ive made an animated gif to show the issue properly, please excuse the cracked iphone screen :)))