The AxHost.BackColorChanged event is not supported by the System.Windows.Forms.AxHost class.
If you attempt to add or remove a handler for the AxHost.BackColorChanged event, a NotSupportedException is thrown. The events derived from the System.Windows.Forms.Control class are not supported by the System.Windows.Forms.AxHost class. The events exposed by the ActiveX control when the System.Windows.Forms.AxHost wrapper is created are the events that should be used.