Yes! I see it especially when the leaves are small, and when the plant is just coming up.You can see the purple in the leaves of the purple potato plant.
I have lots of volunteer potatoes this year, and I'd say over half are purples. I plan to let them grow, as they did well last year. I might try the "sneak a tater" move when they bloom, too. I'm ready for some more stuff from the garden. And it's a long time until tomatoes.