Augustine of Hippo
Catena Aurea · Markusevangelium 15
And the soldiers led him away into the hall, called Prætorium; and they call together the whole band. And they clothed him with purple, and platted a crown of thorns, and put it about his head, And began to salute him, Hail, King of the Jews! And they smote him on the head with a reed, and did spit upon him, and bowing their knees worshipped him. And when they had mocked him, they took off the purple from him, and put his own clothes on him.
(de Con. Evan. iii. 9) But we must understand that the words of Matthew, they put on him a scarlet robe, Mark expresses by clothed him in purple; for that scarlet robe was used by them in derision for the royal purple, and there is a sort of red purple, very like scarlet. It may also be that Mark mentions some purple which the robe had about it, though it was of a scarlet colour.