Halloween originated as a Celtic celebration of Samhain, when spirits were thought to return to Earth. Common Halloween symbols include ghosts, witches, cats, bats, and other scary figures associated with death, like vampires and blood. The colors orange and black represent Halloween - orange for pumpkins and autumn, and black for death. A famous Halloween custom is trick-or-treating, where children go door-to-door saying rhymes and asking for sweets.