Adam Clarke on Luke 23:11

A gorgeous robe - Εσθητα λαμπραν. It probably means a white robe, for it was the custom of the Jewish nobility to wear such. Hence, in Rev 3:4, it is said of the saints, They shall walk with me in White (garments), because they are Worthy. In such a robe, Herod, by way of mockery, caused our Lord to be clothed; but, the nobility among the Romans wearing purple for the most part, Pilate's soldiers, who were Romans, put on Jesus a purple robe, Mar 15:17; Joh 19:2; both of them following the custom of their own country, when, by way of mocking our Lord as a king, they clothed him in robes of state. See Bishop Pearce.