This recipe shows how to change the color of a navigation bar.
To change the color of the navigation bar, set the TintColor property of the UIViewController’s NavigationBar property:
this.NavigationController.NavigationBar.TintColor = UIColor.Red;
To reset the color to its default, set this value to null:
this.NavigationController.NavigationBar.TintColor = null;
iOS 5 has introduced an additional way to style elements via the Appearance static property on most UIKit classes. You can style all the navigation bars in your application at once with this line:
UINavigationBar.Appearance.TintColor = UIColor.Blue;