Updating changes to the the MainPage from a ContentView

I am new to .net MAUI. Here is my MainPage with and Absolutelayout named mybackscreen.
I created a ContentView User Control named myOptions and added it to the MainPage.

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         xmlns:Controls="clr-namespace:Kone.Controls"
         x:Class="Kone.MainPage" x:FieldModifier="public">

<AbsoluteLayout x:Name="mybackscreen" 
                x:FieldModifier="public" 
                BackgroundColor="Red" >
    
<Controls:Options x:Name="myOptions" x:FieldModifier="public" IsVisible="true" AbsoluteLayout.LayoutFlags="PositionProportional" AbsoluteLayout.LayoutBounds="0.99, 0.02, 270, 375" />

There is a button on the ContentView myOptions when clicked should change the backgroundcolor of "mybackscreen" but it doesnt change. I know this has to do with setting an instance of the MainPage.

    MainPage newinstance = new MainPage();
    newinstance.mybackscreen.BackgroundColor = Colors.Black;

I must be missing some code to update or refresh the UI View because nothing changes. This is what i used in my WinForm App but wasnt able to convert so i just simplified it with the above code:

        public static MainPage Default
    {
        get
        {
            if (defaultInstance == null)
            {
                defaultInstance = new MainPage();
                defaultInstance.FormClosed += new FormClosedEventHandler(defaultInstance_FormClosed);
            }

            return defaultInstance;
        }
        set
        {
            defaultInstance = value;
        }
    }

    static void defaultInstance_FormClosed(object sender, FormClosedEventArgs e)
    {
        defaultInstance = null;
    }

As Jason said, you can create an event to achieve it:

Options.xaml:

<ContentView ...
             x:Class="Options">
    <VerticalStackLayout>
        <Button Text="Click"
                x:Name="btn"
                Clicked="btn_Clicked"/>
    </VerticalStackLayout>
</ContentView>

Options.xaml.cs:

public partial class Options : ContentView
{
    public event EventHandler OptionsChanged;
    public Options()
    {
        InitializeComponent();
    }

    private void btn_Clicked(object sender, EventArgs e)
    {
        OptionsChanged.Invoke(this, EventArgs.Empty);
    }
}

Create event OptionsChanged and call it in method btn_Clicked. Then back to MainPage.xaml:

<ContentPage ...>
    <AbsoluteLayout x:Name="mybackscreen"
                    BackgroundColor="red">
        <Controls:Options x:Name="myOptions"
                          OptionsChanged="btn_Clicked"
                          .../>
    </AbsoluteLayout>
</ContentPage>

Let method btn_Clicked of MainPage subscribe to OptionsChanged of Options. And here is MainPage.xaml.cs:

public partial class MainPage : ContentPage
{
    public MainPage()
    {
        InitializeComponent();        
    }
    private void btn_Clicked(object sender, EventArgs e)
    {
        mybackscreen.BackgroundColor = Colors.Black;
    }
}

I found this works without any downside so far:

public partial class MainPage : ContentPage

{

public static MainPage Default;

public MainPage()
{
 InitializeComponent();
    Default = this;
            
}
public static void ColorChange(FieldInfo colorField)// Back color of back screen
{  
    Default.mybackscreen.BackgroundColor = (Color)(colorField.GetValue(null));
}

Calling a static method from another class allows the main ui to change by using Default.