WPF change background color of button when window is disabled

I have a button with transparent background in a wpf window.

The problem is that when I open another window with a .showdialog, the form becomes disabled just like the button, causing the button to whiten (and stick out like a sore thumb); the same thing happens with the listview and textbox controls. Labels and group boxes are not affected in this way and remain in order.

How can I keep the transparency color of button, list and text boxes when disabled?

Thanks Rob