Those taking part in processions are to walk bare-headed (weather permitting), two and two, in decent costume, and with reverent mien; clergy and laity, men and women, are to walk separately. The cross is carried at the head of the procession, and banners embroidered with sacred pictures in places where this is customary; these banners must not be of military or triangular shape. Violet is the prescribed colour for processions, except on Corpus Christi, or on a day when some other colour is mandated. The officiating priest wears a cope, or at least a surplice with a violet stole, while other priests and clergy wear surplices.