How can I set the background for the splitter in DockingManager?

// This code demonstrates how to set the Splitter Background for the DockingManager:
<Window x:Class="DockingManager_floatwindowsample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:syncfusion="http://schemas.syncfusion.com/wpf"
        Title="MainWindow" Height="350" Width="525">
    <Grid x:Name="Grid1">
       <syncfusion:DockingManager x:Name="Dock1"  UseDocumentContainer="True" SplitterBackground="Brown" >
         <ContentControl syncfusion:DockingManager.Header="Dock1"
                         syncfusion:DockingManager.State="Dock">                 
         </ContentControl>
         <ContentControl syncfusion:DockingManager.Header="Dock2"
                          syncfusion:DockingManager.State="Dock"
         </ContentControl>
         <ContentControl syncfusion:DockingManager.Header="Dock3"
                          syncfusion:DockingManager.State="Dock">
         </ContentControl>
         <ContentControl syncfusion:DockingManager.Header="Dock4"
                          syncfusion:DockingManager.State="Document">
         </ContentControl
       </syncfusion:DockingManager>
    </Grid>
</Window>

// This code demonstrates how to set the Splitter Background for the DockingManager:
using Syncfusion.Windows.Tools.Controls;
namespace DockingManager_floatwindowsample
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            DockingManager Docking = new DockingManager();
            Docking.SplitterBackground = Brushes.Brown;
            Docking.UseDocumentContainer = true;
            ContentControl content1 = new ContentControl();
            DockingManager.SetHeader(content1, "Dock1");
            DockingManager.SetState(content1, DockState.Dock);
            ContentControl content2 = new ContentControl();
            DockingManager.SetHeader(content2, "Dock2");
            DockingManager.SetState(content2, DockState.Dock);
            ContentControl content3 = new ContentControl();
            DockingManager.SetHeader(content3, "Dock3");
            DockingManager.SetState(content3, DockState.Dock);
            ContentControl content4 = new ContentControl();
            DockingManager.SetHeader(content4, "Dock4");
            DockingManager.SetState(content4, DockState.Document);
            Docking.Children.Add(content1);
            Docking.Children.Add(content2);
            Docking.Children.Add(content3);
            Docking.Children.Add(content4);
            Grid1.Children.Add(Docking);          
        }
    }
   }