How can I apply the brush color for the LeftFloatWindowBorder?

// This code demonstrates how to set the LeftFloatWindowBorderBrush 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" LeftFloatWindowBorderBrush="Red" >
         <ContentControl syncfusion:DockingManager.Header="Dock1"
                         syncfusion:DockingManager.State="Float">                   
         </ContentControl>
         <ContentControl syncfusion:DockingManager.Header="Dock2"
                          syncfusion:DockingManager.State="Dock">
         </ContentControl>
       </syncfusion:DockingManager>
    </Grid>
</Window>

// This code demonstrates how to set the LeftFloatWindowBorderBrush 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.LeftFloatWindowBorderBrush = Brushes.Red;
            Docking.UseDocumentContainer = true;
            ContentControl content1 = new ContentControl();
            DockingManager.SetHeader(content1, "Dock1");
            DockingManager.SetState(content1, DockState.Float);
            ContentControl content2 = new ContentControl();
            DockingManager.SetHeader(content2, "Dock2");
            DockingManager.SetState(content2, DockState.Dock);
            Docking.Children.Add(content1);
            Docking.Children.Add(content2);
            Grid1.Children.Add(Docking);             
        }
    }
}