Improve the way to format easily summary task. Currently you need to cast all elements of summary element to change the BackColor. 

Resolution: 
There are three properties added to GanttViewSummaryElement which allow access to the inner elements: LeftElement, MiddleElement and RightElement. 
Please take a look at the code example: 
private void radGanttView1_GraphicalViewItemFormatting(object sender, GanttViewGraphicalViewItemFormattingEventArgs e)
{
    GanttViewSummaryItemElement element = e.ItemElement as GanttViewSummaryItemElement;
    if (element != null)
    {
        GanttViewSummaryElement summary = element.TaskElement as GanttViewSummaryElement;
        summary.LeftElement.BackColor = Color.Blue;
        summary.RightElement.BackColor = Color.Blue;
        summary.MiddleElement.BackColor = Color.LightGreen;
        summary.ProgressIndicatorElement.BackColor = Color.Red;
    }
}