From iOS 5 onwards we have to set title text color and font of navigation bar using titleTextAttribute Dictionary(predefined dictionary in UInavigation controller class reference).
[[UINavigationBar appearance] setTitleTextAttributes:
[NSDictionary dictionaryWithObjectsAndKeys:
[UIColor blackColor], NSForegroundColorAttributeName,
[UIFont fontWithName:@"ArialMT" size:16.0], NSFontAttributeName,nil]];
The below tutorial is the best tutorial for customization of UIElements like UInavigation bar, UIsegmented control, UITabBar. This may be helpful to you
http://www.raywenderlich.com/4344/user-interface-customization-in-ios-5