How to set the Header Background color on a TDI child in WPF DocumentContainer ?

<Window.Resources>
        <LinearGradientBrush x:Key="Aero.TabBackgroundBrush" StartPoint="0,0" EndPoint="0,1">
            <LinearGradientBrush.GradientStops>
                <GradientStop Color="#FFECF5FC" Offset="0" />
                <GradientStop Color="#FF98B4D2" Offset="1" />
            </LinearGradientBrush.GradientStops>
        </LinearGradientBrush>
        <local:SelectedTabItemBackgroudConverter x:Key="SelectedTabItemBackgroudConverter"></local:SelectedTabItemBackgroudConverter>
    </Window.Resources>
   <syncfusion:DocumentContainer x:Name="Doccontainer" Mode="TDI" >
         <syncfusion:DocumentContainer.DocumentTabControlStyle>
             <Style TargetType="syncfusion:DocumentTabControl">
                 <Setter Property="TabItemSelectedBackground" Value="{Binding Path=SelectedItem,RelativeSource={RelativeSource Self},Converter={StaticResource SelectedTabItemBackgroudConverter}}"></Setter>
             </Style>
           </syncfusion:DocumentContainer.DocumentTabControlStyle>
      <ContentControl x:Name="child1"  syncfusion:DocumentContainer.Header="Document1"  >
         <syncfusion:DocumentContainer.DocumentTabItemStyle>
                   <Style TargetType="{x:Type TabItem}">
                       <Setter Property="Background" Value="Green"/>
                   </Style>
           </syncfusion:DocumentContainer.DocumentTabItemStyle>
        </ContentControl>
        <ContentControl x:Name="child2" syncfusion:DocumentContainer.Header="Document2" >
               <TextBlock Text="This is a document2" />
          </ContentControl>
         <ContentControl x:Name="child3" syncfusion:DocumentContainer.Header="Document3"/>
            <ContentControl x:Name="child4" syncfusion:DocumentContainer.Header="Document4"/>
            <ContentControl x:Name="child5" syncfusion:DocumentContainer.Header="Document5"/>
</syncfusion:DocumentContainer>

public class SelectedTabItemBackgroudConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            object background = (LinearGradientBrush)Application.Current.MainWindow.Resources["Aero.TabBackgroundBrush"];
            if (value is TabItem)
                background = (value as TabItem).Background ?? background;
            return background;
        }
        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return value;
        }
    }