self.navigationController?.navigationItem.largeTitleDisplayMode = .always
self.navigationController?.navigationBar.prefersLargeTitles = true
self.navigationController?.navigationBar.largeTitleTextAttributes = [NSForegroundColorAttributeName: UIColor.white]
// unconfirmed but I assume this works:
self.navigationController?.navigationBar.barTintColor = UIColor.white
self.navigationController?.navigationBar.barStyle = UIBarStyle.black