How to set color for NavigationBar background and text in Xamarin.Forms.Android?

Hello everyone,

I want to change the navigation bar background color and text color. But i don't know how to set it.
I can only set the bar background color in App.cs file.

MainPage = new NavigationPage(new MainPage()) { BarBackgroundColor = Color.Green };

But i want to change this setting in other page.

var work=new WorkPage();
this.Navigation.PushAsync(work);

Actuall, i want to set the BarBackgroundColor to Red when the WorkPage is show.

I set it in other page as this.
`public partial class WorkPage : ContentPage
{
public WorkPage ()
{
InitializeComponent ();

    var baseModel= new RootViewModel ();
    baseModel.BarBackgroundColor = Color.Red;
    baseModel.BarTextColor = Color.Accent;
    this.BindingContext = baseModel;

    this.SetBinding (NavigationPage.BarBackgroundColorProperty, "BarBackgroundColor");
    this.SetBinding (NavigationPage.BarTextColorProperty, "BarTextColor");
}

}`

public class RootViewModel:BindableObject  
{
    public Color BarBackgroundColor{get;set;}
    public Color BarTextColor{get;set;}
    public string BarTitle{get;set;}
}

but it did not work for Android. Can anyone help me for this? Thanks in advance!