These lovely beans are dark purple, but bright green just under the skin. The purple pigment is a built-in indicator of done-ness in the kitchen – the whole bean turns green when ready to eat. Often I steam my beans, or put them through a light boil. The purple slowly fades to green. When we sauteed them the other day (with our freshly harvested garlic – YUM!), some spots were cooking and others were not – creating these gorgeous purple-and-green patterns on the beans. We left some of them with purple blotches, but they were indeed not quite cooked!