Xamarin Forms control the color/title of the header bar

If you want to use one color for all NavigationPage elements you can do it easier. Add global style to app for a NavigationPage

<?xml version="1.0" encoding="utf-8"?>
<Application xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    x:Class="My.App">
    <Application.Resources>
        <!-- Application resource dictionary -->
        <ResourceDictionary>
          <!-- Pallete -->     
          <Color x:Key="primary-back-title-color">#4a148c</Color>
          <Color x:Key="primary-title-color">#FFFFFF</Color>
          <!-- Pallete-end -->  
          <Style ApplyToDerivedTypes="true" TargetType="NavigationPage">
                <Setter Property="BarBackgroundColor" Value="{StaticResource Key=primary-back-title-color}"/>
                <Setter Property="BarTextColor" Value="{StaticResource Key=primary-title-color}"/>
          </Style>
        </ResourceDictionary>
    </Application.Resources>
</Application>

Now you can do:

        void OnTappedProfile(object sender, System.EventArgs e)
        {
            Navigation.PushAsync(new Profile());
        }

Where Profile is ContentPage

Set the BarBackgroundColor of the NavigationPage. You can do something like this (in the most basic example sense):

        var nav = new NavigationPage
        {
            Title = "Detail"
        };
        nav.PushAsync(new ContentPage() { Title = "Home" });
        nav.BarBackgroundColor = Color.MediumPurple;

        var mdp = new MasterDetailPage()
        {
            Master = new ContentPage()
            {
                Title = "Master"
            },
            Detail = nav
        };
        MainPage = mdp;

The title of the ContentPage being presented by the NavigationPage is what will show the title on that bar.

The BarBackgroundColor is a property of the NavigationPage class:

public App()
{
    MainPage = new NavigationPage(new Page1())
    {
        BarBackgroundColor = Color.FromHex("#ff5300"),
        BarTextColor = Color.White,
    }; 
}