The horse is white, which shows that it is an instinctual impulse which has its natural direction toward consciousness. The sun god’s chariot in Greece and in Rome was pulled by white horses, while the chariots of the night or the moon were pulled by dark horses.
Von Franz establishes the white horse as an instinctual force whose color encodes a directional orientation toward consciousness, solar order, and the Olympian world, against dark horses representing the nocturnal and chthonic.
, Shadow and Evil in Fairy Tales, 1974thesis