How can I change the background of child MenuItems?

Question

WPF

In the picture, I managed to make a transparent background for the main menu and for MenuItem, but I don’t know how for the child ones. Help me please.
You need to make it transparent instead of white.

<Menu x:Name="menu" Height="26" VerticalAlignment="Top" Background="{x:Null}" Foreground="{x:Null}">
            <MenuItem  Header="Настройки" Height="26" Foreground="Lime" RenderTransformOrigin="0.5,0.5" Background="Transparent" BorderBrush="Transparent" Padding="6,0" UseLayoutRounding="False">
                <MenuItem Header="Свойства" Foreground="Lime" RenderTransformOrigin="0.5,0.5" Background="Transparent" BorderBrush="Transparent" AutomationProperties.IsColumnHeader="True"/>
                <MenuItem Header="О программе" Foreground="Lime" RenderTransformOrigin="0.5,0.5" Background="Transparent" BorderBrush="Transparent" AutomationProperties.IsColumnHeader="True"/>
                <Separator/>
                <MenuItem Header="Выход" Foreground="Lime" RenderTransformOrigin="0.5,0.5" Background="Transparent" BorderBrush="Transparent" AutomationProperties.IsColumnHeader="True"/>
            </MenuItem>
        </Menu>

Answer 1

You need to redefine the menu element template - just add this code to Window.Resources and that's it, you don't even need to add anything to <Menu>. "MenuItem.TopLevelHeaderTemplateKey" - standard template name

<ControlTemplate x:Key="{x:Static MenuItem.TopLevelHeaderTemplateKey}" TargetType="{x:Type MenuItem}">
    <Border Name="Border" >
        <Grid>
            <ContentPresenter Margin="6,3,6,3" ContentSource="Header" RecognizesAccessKey="True" />
            <Popup Name="Popup" Placement="Bottom" IsOpen="{TemplateBinding IsSubmenuOpen}" AllowsTransparency="True" Focusable="False" PopupAnimation="Fade">
                <Border Name="SubmenuBorder" SnapsToDevicePixels="True" Background="Transparent">
                    <StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" />
                </Border>
            </Popup>
        </Grid>
    </Border>
</ControlTemplate>

The solution is from here . They also use triggers there, but not necessarily here.