How to set MouseOver event/trigger for border in XAML?

Question

I want the border to turn green when the mouse is over it and then to return to blue when the mouse is no longer over the border.

I attempted this without any luck:

Answer 1

Yes, this is confusing...

According to this blog post, it looks like this is an omission from WPF.

To make it work you need to use a style:

I guess this problem isn't that common as most people tend to factor out this sort of thing into a style, so it can be used on multiple controls.