Hmmm. I wonder why I remember the name?
It's odd that something named "purpureus" would have white flowers, but according to Wikepedia, they sometimes do.
The one that I saw (and liked) had purple flowers, but I heard that they can be poisonous, so why would I grow a bean that I cannot eat - except for the name.
They can be perennial in certain climates, so that would be a plus for an ornamental bean.
Linda