In section 1.2 of Victorinus’ Commentary on the Apocalypse, we read:
His antiquity and immortality, the source of majesty, are shown by with a white head. For the Head of Christ is God. And with white hair are the multitude of wearers of white (the newly baptized), like wool, because of the sheep, like snow, because of the innumerable crowd of candidates (catechumens) given by Heaven. Eyes like a flame of fire. These are the commandments of God, giving light to those who believe, (but) burning the unbelievers.
Now, part of this explanation may seem puzzling, particularly this: like snow, because of the innumerable crowd of candidates given by Heaven.
It helps to know a little about Roman culture here. Those who put themselves up for election to an office wore a particular toga called the toga candida. This was a toga of the regular shape and size, draped in the usual manner, but was distinguished by being well-bleached and then chalked to make it brilliantly white. Thus, the wearer of such a toga, the candidate (candidatus), shone as brightly as newfallen snow, and was easily distinguished in a crowd. Victorinus here is playing at words, by using candidates (candidatorum) here in a general sense as we do, to refer to anyone in line for a potential position, and in a way that makes use of the word’s very particular connotation of brilliant whiteness. In this case, he describes the catechumens as candidates for becoming Christians. It’s a particularly apt and striking image.