These are the same potatoes. I cut them in half, raw, to show you what the uncooked flesh looks like. Pretty cool-looking! You can see that the "black" ones on the right have better, darker and more uniform color.
Here they are the following day after cooking and storing in the fridge overnight. The light ones actually got lighter, while the dark ones got darker!
So there you have it: my very unscientific comparison of the two purple potato types available in my neighborhood. In case you were interested. ^_^
Almost forgot to mention: they look super pretty in bento!