Customization not working

I can't customize the navigation bar... In my AppDelegate.m

RFAboutViewController *aboutView = [[RFAboutViewController alloc]initWithAppName....
aboutView.navigationViewBackgroundColor = [UIColor blackColor];
aboutView.navigationBarTitleTextColor = [UIColor whiteColor];
.
.
.
 _aboutNavigation = [[UINavigationController alloc]initWithRootViewController:aboutView]; [self.window.rootViewController presentViewController:_aboutNavigation animated:YES completion:nil];

But nothing changes...