Many prisoners of consequence became a valuable accession to the spoil; and Priscus, a brother of the late emperor Philip, blushed not to assume the purple, under the protection of the barbarous enemies of Rome.What does it mean to assume the purple?
The Decline and Fall of the Roman Empire Volume 1 Chapter 10
In antiquity, as is still true today, different statuses are associated with specific colors. At a funeral in the West, mourners expect the widow to wear black or some other dark, somber hue. A virginal bride in the U.S. is expected to wear white and if someone obviously not a virgin wears a white gown, it occasionally leads to snickering. In Greek artwork about the Trojan War, a certain type of conical cap, which we call a Phrygian cap, identifies its wearer as Trojan. In Republican Rome, freed slaves had red Phrygian caps. Also in Republican Rome, after a great military victory, a general's troops might proclaim the leader imperator, and so help him on his way to the granting of a triumph. The cloak that identified the imperator was purple.
During the period of the Roman Empire, the title imperator came to be used for the one-man ruler or princeps. We call him emperor. Assuming the purple meant putting on the purple cloak of the imperator. This signalled the fact that the person so doing had become emperor.
Here's another passage about assuming the purple, from an abridgment of Eutropius Roman History. Book IX
Gallienus, who was made emperor when quite a young man, exercised his power at first happily, afterwards fairly, and at last mischievously. In his youth he performed many gallant acts in Gaul and Illyricum, killing Ingenuus, who had assumed the purple, at Mursa, and Regalianus
By around the time of Constantine, emperors wore diadems in imitation of the Persian kings. Today we speak of the crowning of kings. The crowning of a king is very much like the emperor assuming the purple.
For more information on purple and status, see:
- "On Status Symbols in the Ancient World," by Meyer Reinhold. The Classical Journal, Vol. 64, No. 7. (Apr., 1969), pp. 300-304.
- "The Minoan Origin of Tyrian Purple," by Robert R. Stieglitz. The Biblical Archaeologist, Vol. 57, No. 1. (Mar., 1994), pp. 46-54.