I would like to know how to change the background color of the AppShell menu buttons.

Is there a property I could use?

Is there a template that I could customize? like this :
(App.xaml of PlatformsWindows)

    <maui:MauiWinUIApplication.Resources>
        <DataTemplate x:Key="MauiAppTitleBarTemplate">
            <Grid>
                <Border Canvas.ZIndex="1" VerticalAlignment="Stretch" Background="#0366d6" Margin="0,0,0,0"></Border>
            </Grid>
        </DataTemplate>
    </maui:MauiWinUIApplication.Resources>

Image below of what I want to change the background color of:

I expect this result :