title: Change Color of navigationBar of just UIActivityViewController
body: <p>How do you change the colour of only the UIActivityViewController?</p>
  
  <p>I want to change the colour of just the UINavigationBar of the UIActivityViewController using something like:</p>
  
  <pre><code>self.activityViewController.navigationController.navigationBar.barTintColor = [UIColor greenColor];
  </code></pre>