But, as with all this stuff, your post creates ever more questions. What do all these mysterious rectangles actually do? And how many other obscure places hide myriad other controls? It seems like in order to figure out what is going on, one’s only recourse is to dump a copy of the template into app.xaml and then pour over it.

To do something as simple as changing the background color of the selected item seems to take a ridiculous amount of time.

Why does it have to be soooo difficult to get the info we need to actually style a combo box (or other control)?