When you use a style for a form and you have no background color set in that style the header part is white instead of the default background.
When you change it to title header then it uses the default background.
This behaves the same in Table View, List View and Record View.
When you remove the style assignment then it behaves correctly.
Well I encounter it with version 2.1.2 (Mac OS X).
I did a quick test just now on 2.2b3 (Windows XP) and it seems to work correctly.
So it seems they fixed this issue.
Lets hope they keep this fix when they try to fix the other style issues
Anyway..I guess I should have checked with the latest beta first before posting this issue.