Why is it that the pope’s cassock is white while the clothes of other clergymen are usually black?
The custom of popes wearing white cassocks dates to Pope St. Pius V, a Dominican who chose to continue wearing the Dominican white habit as pope. Successive popes continued the custom, and it is now the traditional color of the pope’s clothing.
Now I don’t know the names for all the garments, I apologise for that.
Julius II, pope 1503 – 1513
**Pius V, pope 1566 – 1572, who supposedly introduced the white papal cassock. ** It’s not really a cassock, though. It’s white, but so were the clothes of the previous popes. It’s much wider than a cassock, and made by thinner cloth.
Pius VII, pope 1800 – 1823. A bit wide and probably made of silk, but this looks very much like a cassock - although not really like a Dominikan habit.
Pius IX, pope 1846 – 1878. The first pope to be photographed, in a white cassock that looks very much like what the popes of today are wearing. In all white - that’s new. OTOH we don’t know how many of the previous popes who usually wore all white, and donned that red cape just for gala.
Pius X, pope 1903 – 1914
Did Pius V actually use his white Dominikan habit as a pope? Well… maybe on ordinary weekdays, but not when posing for painters? Anyway, it seems the papal clothes have developed little by little. Maybe Pius IX, or one of his predecessors, thought a white cassock would be a good idea - and then they pointed to Pius V, although he wore what was expected of him at grand occasions and wore his old white cassock just around the house?
I’m just speculating. If someone actually knows something about Pius V and his white cassock - not just that which is always repeated - that would be really interesting.