I'm creating the scroller in code so it looks like this:
scroller.SetValue(StyleManager.ThemeProperty, StyleManager.ApplicationTheme);
Basically I just want the scrollbar to match other Office_Blue themed controls. I've attached a screenshot showing the problem. The grid at the bottom obviously has the blue scroll bar and also the TextBox in the top left region does (when I set the style explicitly) but the ScollViewer it sits within does not even though the above code is being run.