Change WF4 ActivityDesigner theme

I want to change my rehosted activities look to:

Already tried ActivityDesignerTheme

Need to do it without using WorkflowViewElement because I don't want to lose it's behaviors (breakpoint, expanding).

If it's not possible, is there a way to change ActivityDesigner header background color?

@Will
I was annoyed too by the default behavior of the ActivityDesigner header when editing the DisplayName (especially the part where it positions the caret at the beginning of the string). I used Reflector to peek (System.Activities.Presentation.dll) at the implementation and I noticed that some of this behavior is defined in OnApplyTemplate. By just overriding this method in my custom designer class and NOT calling base.OnApplyTemplate(), I was able to make the DisplayName read only in the header (in my case that was all I needed, but I think one can play with some custom event handlers in there and tweak the behavior).

@Davi Fiamenghi
Digging around some more with Reflector in the same assembly, I found the controls used in OnApplyTemplate defined under system/activities/presentation/workflowelementdesignerdefaulttemplate.baml (System.Activities.Presentation.g.resources). That seems to be the default control template used for ActivityDesigner (<ControlTemplate x:Key="WorkflowElementDesignerDefaultTemplate" x:Uid="ControlTemplate_1" ControlTemplate.TargetType="{x:Type swd:ActivityDesigner}">). I guess one way to change the header color would be to try to "re-create" this template in your application and set it explicitly in your custom activity designer. Of course it's more involved than just copying it, since it appears to be referencing other resources defined in that assembly.

Hope this helps.