By default, the OwnerDraw property is False. Use the OwnerDraw property to perform your own drawing inside the panel. If the OwnerDraw property is True, the control fires the OwnerDrawStart event just before erasing and painting the panel. You can use the Transparency property to apply semi-transparent colors to the panel's content so both paintings are shown the default and your owner. The control fires the OwnerDrawEnd event when the control ends painting an owner draw panel. Use the OwnerDrawStart event to perform painting before control's default painting, and use the OwnerDrawEvent to perform your paintings after default painting is done.

The first panel in the screen shot shows a curve being drawn using the OwnerDrawStart event and still performing the default painting, as the text is painted as semi-transparent.