miFileNew = new MenuItem( "&New Book..." );
miFileNew.OwnerDraw = true, 
miFileNew.Click += new EventHandler(MenuFileNewOnClick);
miFileNew.DrawItem += new DrawItemEventHandler(MenuOnDrawItem);
miFileNew.MeasureItem += new MeasureItemEventHandler(MenuOnMeasureItem);
Menu.MenuItems[index].MenuItems.Add(miFileNew);
соответственно есть:
void MenuOnMeasureItem(object obj, MeasureItemEventArgs miea)
{
   miea.ItemWidth =  75 ;
   miea.ItemHeight =  16 ;
}
void MenuOnDrawItem(object obj, DrawItemEventArgs diea)
	{
   	diea.Graphics.FillRectangle(Brushes.White, diea.Bounds);
diea.Graphics.DrawString(((MenuItem)obj).Text, Font, Brushes.Black,  10 , diea.Index* 16 ); 

  if ((diea.State & DrawItemState.Selected) !=  0 ) 
{
  diea.Graphics.FillRectangle(new SolidBrush(Color.FromArgb( 100 , Color.LightSteelBlue)), diea.Bounds);
 }
}