Every Priest (and Bishop) is supposed to switch to white from Pascha until Pentecost. Officially the vestment change is made on Holy Saturday morning. After Pentecost it goes back to normal.
Yes, but it is not liturgical vestments that are under discussion here, but rather clerical street garb, specifically Metropolitan Jonah`s.
Light-colored, especially white, exorasa fell out of general use about 200 years ago. I've read, although not seen it confirmed, that the Turks used to force Orthodox priests to wear white instead of black. That way the Muslim clerics would look crisp in their black robes and the Christians would look dirty.
Anyway, the Slavs adopted the practice of wearing white, and, true to form, the Russians in particular turned it into a very stratified system that corresponded to the clerical caste structure. You could tell a clergyman's rank and office by the color and marking on his podriasnik and riassa. Different color combinations, including different types of lining on each, meant different things.
This produced the famous distinction between "black" (i.e. monastic) and "white" (i.e. parish) clergy, which persisted in the Russian tradition until fairly recently, and included other distinctive markers (e.g. "white" clergy wore goatees, not beards). Fr Schmemann used to wear a white cassock and, in general, comported himself like a white clergyman should according to the pre-Revolutionary standards.
Metropolitan Jonah's riassa, however, looks to be of very inferior quality. Not at all as dignified as those worn by the Patriarch of Romania.