Oscar Wilde may or may not have said Niagara Falls was a honeymooning bride’s second biggest disappointment, but I think of that whenever I see purple green beans. It’s been years since I first got taken in by the color at the Greenmarket only to watch the beans turn ordinary as they cooked. This week, though, I kept reading/hearing people bummed to learn the color does not last. On Wednesday it was funny when a woman picking out only green and yellow beans was asked by her companion why she was passing up the novelty. “Remember what happened when I tried to make a three-bean salad?” Harold McGee writes that the color comes from anthocyanins, pigments similar to chlorophyll (green) and carotenoids (orange or yellow) that are stored only in the outer layer of the beans. Cooking damages the cells and the color is “diluted to invisibility.” The obvious solution is to skip the cooking. Or skip the beans and buy purple peppers. Those are not just colorful but have fabulous flavor, almost nutlike.