STORAGE. If there are any leftovers you can refrigerate them and eat them the next day. The color and the flavor both hold up well for 24 hours or so. The dish is best when eaten at room temperature, so remember to take them out 60-90 minutes before eating to allow the beans to come to temperature.
SUBSTITUTIONS. This sauce works well with all sorts of vegetables. Don't be afraid to experiment. My fallback when beans are out of season is some variety of hearty leafy greens like spinach or Swiss chard.