title: How to modify Expander button background only? WPF
body: <p>I have an Expander placed on a window with a blue background and I would like to make the button for the expander another color than the default (blue, which it is receiving from the window).  When I modify the background property of the expander it changes the entire expander, header and all to the new color.  However, I would like only the button itself to change.  Could anyone point me to the right property that I am looking for?
  Thank you</p>