Background color settings of the button surface when the mouse pointer is over the button area.
If the SpecialEffect property is set to a value different from SPECEFF_NONE (0) this property would affect only the internal portion of the button surface.
If this color is left undefined, the ColorSurfaceNormal property settings are kept: you can swap the colors of the internal portion with the colors of the external portion through the SwapEffectsColors property.
This property is ignored when the Surface property is set to SURFACE_VISTA_AERO, SURFACE_OFFICE_2003, SURFACE_OFFICE_2007 and no special effect has been set through the SpecialEffect property.
This property encapsulates the functionality of the SurfaceColor object and the ISurfaceColor COM interface.
For further details about colors change, see the How to change the button colors section.