SetEnabledOn
virtual void SetEnabledOn(BPicture* picture);
fRefreshButton->SetEnabledOn(ButtonPicture(true, REFRESH_BUTTON_PICT));
fColorButton->SetEnabledOn(ButtonPicture(true, COLOR_BUTTON_PICT));
fDensityButton->SetEnabledOn(ButtonPicture(true, DENSITY_BUTTON_PICT));