title: How to change backGround color in Xamarin forms NavigationPage
body: <p>I'm trying to change the background color of navigationBar in navigationPage I'm using this code:</p>
  <pre><code>using System;
  using System;
  using Xamarin.Forms;
  using System.Collections.Generic;
  using System.Text;
  using System.Linq;
  using System.Threading.Tasks;
  namespace P
  {
  public class App : Application
  {
      public App ()
      {
   MainPage = new NavigationPage(new LoginPage());
      }
      protected override void OnStart ()
      {
      }
      protected override void OnSleep ()
      {
      }
      protected override void OnResume ()
      {
          // Handle when your app resumes
      }
     }
    }
  </code></pre>
  <p>how can I do it?</p>