We grow Provider green beans. They grow well in our clay and cool soil without any issues. We get lots of beans of each plant every summer. Usually they start becoming available in mid July as we seed right into the soil.
We do grow Purple Royalty, so if you want the same great flavor in a purple bean, then just ask for it. When cooked, the Purple Royalty does turn green. So be sure to look for them if you are interested.