Unable to use Style in xaml #231

This is my first project using Stylet so I am probably missing something. I am opening a number of views that open other views, all of the views have a button that opens another view and a GoBack button. When I have all of the styling information in each button the project compiles and runs just fine.
When I pull the styling values out into Styles.xaml and use the Style tag

I get the following error message
"{DependencyProperty.UnsetValue}" is not a valid value for property 'Foreground'.