<Shell
...
  BackgroundColor="{StaticResource Background}"
  FlyoutBackground="{StaticResource Background}"
  FlyoutBackdrop="{StaticResource PrimaryLighter}"
  FlyoutIcon="{StaticResource HamburgerMenu}"
  Shell.ForegroundColor="Red">

  <Shell.Resources>
    <ResourceDictionary>
      <FontImageSource x:Key="HamburgerMenu" FontFamily="FontIcons" Glyph="{StaticResource BurgerMenu}" Size="20"
                       Color="{StaticResource Primary}">
      </FontImageSource>
    </ResourceDictionary>
  </Shell.Resources>

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MyPage.Views.Info.MyPage"
             BackgroundColor="{StaticResource Background}"
             Title="MyPage">

  <ContentPage.Resources>
    <ResourceDictionary>
      <FontImageSource x:Key="BackButton" FontFamily="FontIcons"
                       Glyph="{StaticResource LeftArrow}"
                       Size="20"
                       Color="{StaticResource Primary}"></FontImageSource>
    </ResourceDictionary>
  </ContentPage.Resources>

  <Shell.BackButtonBehavior>
    <BackButtonBehavior IconOverride="{StaticResource BackButton}"></BackButtonBehavior>
  </Shell.BackButtonBehavior>