A6Ms started the war in a scheme of all over light olive grey with a black cowling. However in many books and plastic kits this colour is incorrectly shown as a very pale grey and this may be what you mean by white.
Land based A6M squadrons often field-applied camo paint to their aircraft's upper surfaces as on this skin. Late war A6Ms were factory painted with green upper surfaces, the colour of which varied from factory to factory.