如何将树荫赋予telerik mvc组合框中特定索引的列表项

Code:

  @( Html.Telerik().ComboBox()
    .Name("cmbTest")
    .ClientEvents(events => events
                    .OnOpen("oncmbTestOpen")
                )
    )

   function oncmbTestOpen(e)
   {
        var index = 2;
        // How to give the shade(default orange color) to the list item of particular index(2) in the telerik mvc combo box
   }
  @( Html.Telerik().ComboBox()
    .Nam