White vestments signify purity, light, resurrection, brightness, and rejoicing. And these vestments are being worn at funeral Masses. The priests at funeral Masses preach about how wonderful and great the deceased person was.
Traditionally black vestments were worn at a funeral Mass and the priest preached about judgment, heaven, hell, and purgatory. Very little was said about the deceased persons life.
Black vestments are hardly ever worn anymore. Black vestments signify death and sin. Death is a punishment because of original sin, so mournful vestments are worn at funeral Masses.