The purple filet beans are the very best. More tender than a typical green bean. Yes, they do turn green when blanched in boiling salted water for about four minutes. Pinch off the ends of the beans where they were attached to the plant. After blanching, refresh in ice water and spin them dry. A few minutes before serving, heat the beans in a little butter with salt and pepper. These beans are also very good served cold (after they are blanched and refreshed in ice water) on a salad.