Apparently, making your UINavigationBar requires a (tiny) bit more code than just:
self.navigationController.navigationBar.barStyle = UIBarStyleBlackTranslucent;
After trying hard to change my UINavigationBar colour, and mostly giving up, I found out you have to set its tintColor to nil.
self.navigationController.navigationBar.tintColor = nil;
self.navigationController.navigationBar.barStyle = UIBarStyleBlackTranslucent;
self.navigationController.navigationBar.barStyle = UIBarStyleBlackTranslucent;
