How to set the header Background color on a specific MDI child in DocumentContainer ?

<Window.Resources>

<Style x:Key="headerstyle" TargetType="syncfusion:DocumentHeader">

      <Setter Property="Header" Value="syncfusion:DocumentHeader.Header"/>

        <Setter Property="Background">

             <Setter.Value>

                    <LinearGradientBrush StartPoint="0,0" EndPoint="1,1">

                        <GradientStop Color="#FFD9EDFF" Offset="0"/>

                        <GradientStop Color="#FFC0DEFF" Offset="0.445"/>

                        <GradientStop Color="#FFAFD1F8" Offset="0.53"/>

                    </LinearGradientBrush>

             </Setter.Value>

        </Setter>

</Style>

</Window.Resources>

<syncfusion:DocumentContainer x:Name="Doccontainer" Mode="MDI">

            <ContentControl x:Name="child1" syncfusion:DocumentContainer.Header="Document1" syncfusion:DocumentContainer.DocumentMDIHeaderStyle="{StaticResource headerstyle}">

             </ContentControl>

            <ContentControl x:Name="child2" syncfusion:DocumentContainer.Header="Document2">

                <TextBlock Text="This is a document2"/>

            </ContentControl>

            <ContentControl x:Name="child3" syncfusion:DocumentContainer.Header="Document3"/>

</syncfusion:DocumentContainer>

Style style = this.FindResource("headerstyle") as Style;

child1.SetValue(DocumentContainer.DocumentMDIHeaderStyleProperty, style);