I am trying to set all my tab bar's navigation bars UIBarStyleBlack.
I could also achieve this for the "more" tab bar with this:
tabBarController.moreNavigationController.navigationBar.barStyle = UIBarStyleBlack;
The problem is that when you click its top Edit button to customize the tabs it presents a new modal controller with a standard blue navigation bar, and I can't manage to set it UIBarStyleBlack.
The link has a slightly hackie solution that involves listening to when the modal view will appear.
Colouring fun with moreNavigationController
Until iOS5+ enables us to do it in a cleaner way.