Purple beans?

I bought these absolutely gorgeous purple string beans at the St. Paul farmer's market in Hugo, MN. It was the color. It screamed "impulse buy!". There was a yellow bean in the bunch as well. Extra cuteness to the batch.
I made these as a side dish for some stuffed peppers (also from the farmer's market). I steamed them like I usually do for green beans and what do I get?


Green beans!
They lost all their color and quirkyness.
The flavor was fine, I have no complaints about how they tasted, I just happened to want to dish up some purple beans onto my plate.
Lesson learned.