Their sashimono are a brilliant scarlet; and their helmets, body armour, and their mounted troops' harnesses are the colour of blood.
Also, they are elite warriors, and they have distinctive golden horns on their helmets; some helmets have twisted horns, signifying their owner's higher status. Even Jack, with his Two Heavens technique, had trouble fighting a Red Devil, and Yamato and Akiko had to help him out. But fortunately, Sensei Hosokawa stabbed the Red Devil through the chest from behind. Tragically, during the massacre, Sensei Nakamura was surrounded by Red Devils and was supposedly killed. This triggered a retreat to the inside of the castle, and Taro was soon killed by an Elite Devil.