Hey elkingkade,
I completely forgot about the ‘imperial purple’ robes that Emperor Justinian donned in his depiction. The robe Christ is wearing is also the ‘imperial purple’ that you pointed out, which, as the description details, ‘harkens back to the Roman Emperors.’ I think it is also important to note that Christ wears the same garb as Emperor Justinian which puts them on similar levels – not necessarily saying they are of the same significance but that they have the same power.