Change Android ActionBar Color

Hello,
assumed due to uncertainity by poor documentation, the dark grey bar appearing on Android when pressing a ListViewItem ViewCell (ContextActions) is the ActionBar, how do I Change the Color?
Xamarin documentation "Replacing the Action Bar" does not work and leads to "Attempt to invoke virtual method 'java.lang.CharSequence android.widget.Toolbar.getTitle()' on a null object reference"
Why can't it be simply "easy" and always have to be time-consuming field-exploration?
Any ideas?