(Here's a costume from Greek mythology that doesn't follow the classic style, instead using a witchy black-and-red color scheme and adding wing sleeves and a ruff!)
Scarlet robe with wing sleeves lined with black,and a full, wide ruff of scarlet lined with black high about the neck. A large poppy for a head-dress, and poppies on the toes of the black slippers; red stockings.
Masquerade and Carnival. New York: The Butterick Publishing Company, 1892.
Proserpine is the Romanized Persephone, daughter of Demeter (Ceres) and queen of the underworld as the unwilling bride of Hades (Pluto). The poppies are symbolic of sleep, death, and resurrection and thus particularly appropriate for Proserpine, whose annual descent into the land of death represents the sleep of the earth during winter and whose return brings springtime to the land.