From "Armies and Enemies of Imperial Rome" by Phil Barker, page 58: wall painting in Pompei red tunic, red cloak, red crest. Arrian's Tactica mentions yellow crests for cavalry, scarlet tunics or other colors. Mid Imperial tunics were white/off white with red cloak and crest. The Notitia Dignitatum from the fifth century A.D. shows highly decorative blue and gold shields for guard units. A Trajanic frieze shows a hexagonal guard cavalry shield with four scorpions - the top facing down and the others facing up. There is also a drawing of an oval praetorian shield from the late first century which had a black or dark blue background, white or silver stars, moon and wings, and yellow or gold thunderbolt and lightning flashes.