title: NavigationBar and TabBar background colors are always grey
body: <p>My TabBar and navigationBar are always grey, tried all StackOverflow solutions I found, but none works. They always stay grey. <br>
  This is my <code>AppDelegate</code> code, <code>MenuViewController</code> is a <code>TabBarViewController</code>.</p>
  <pre><code>self.window = UIWindow(frame: UIScreen.main.bounds)
          
          let menuVC = MenuViewController()
          let navigationController = UINavigationController(rootViewController: menuVC)
          
          navigationController.navigationBar.tintColor = .white
          navigationController.navigationBar.barTintColor = .red
          
          window = UIWindow(frame: UIScreen.main.bounds)
          window?.rootViewController = UINavigationController(rootViewController: MainViewController())
          window?.makeKeyAndVisible()
  </code></pre>