How to change Task Flag Color in Microsoft.Office.Interop.Outlook via C#?

Question

Hi i am coding a project with "Microsoft.Office.Interop.Outlook". How can i change flag color according to task importance (High, Medium, Low). i want to change color task importance

   public class MyTecOutLookTasks : IOutLook<MyTasks>
        {
            public Microsoft.Office.Interop.Outlook.TaskItem oTask { get; set; }
            public OutLook._Application outlookApp { get; set; }

            public MyTecOutLookTasks()
            {
                outlookApp = new OutLook.Application();
                oTask = (OutLook.TaskItem)outlookApp.CreateItem(OutLook.OlItemType.olTaskItem);
            }
            #region IOutLook Members
            public void Set(MyTasks myTasks)
            {

                switch (myTasks.EnumSchedulePlusPriority)
                {
                    case MyTecSchedulePlusPriority.High: oTask.SchedulePlusPriority = "High";
                        break;
                    case MyTecSchedulePlusPriority.Medium: oTask.SchedulePlusPriority = "Medium";
                        break;
                    case MyTecSchedulePlusPriority.Low: oTask.SchedulePlusPriority = "Low";
                        break;
                    default:
                        break;
                }
                oTask.Status = OutLook.OlTaskStatus.olTaskInProgress;
                oTask.Importance = Microsoft.Office.Interop.Outlook.OlImportance.olImportanceLow;

            //dosomething
            }