If you're serving beans hot as a side dish, cook them just before serving or reheat them in butter or garlic and olive oil just before serving. Strike is a particularly tasty long, round string bean similar to the beans we used to find in cans, called Blue Lake. Purple beans are delicious, but their fetching color, which makes them easy to spot on the vine, turns to dark green when cooked. Use them the same way you would yellow and plain green beans. Yellow snap beans are becoming more widely available.
Yellow beans are perfect for pickling, as they'll retain their hue in vinegar.
They're also pretty when mixed with plain green beans. Jade beans are among the modern varieties of string beans that don't have a string. They can be served whole or cut up for salads and soups. Romano beans and other flat, wide string beans are especially good in soups, where long cooking coaxes out their characteristic flavor. Haricots verts are tiny, tender string beans worth seeking out.