I'm not familiar with sweet potatoes, but three years ago, I bought purple potatoes and planted them. It wasn't the potato peel that was purple, but the potato itself was that color. When we harvested the harvest in the fall and made mashed potatoes from such potatoes, it looked very unusual.
As a result, my family did not appreciate my experiment. This year, we didn't plant purple potatoes.
By the way, we have been planting purple string beans for several years, but my mother refused to eat them, calling them worms.