Purple Hyacinth Beans

This year, among my many varieties of climbing beans I am growing 'Purple Hyacinth Beans'. In true Matron fashion, I 'liberated' some seeds last Autumn from a garden in Virginia. Actually this picture was taken there last Autumn. My plants this year are growing well amongst the other runner beans, they appear to have an attractive purple veined leaf, I think they will be a late variety. There are signs of the beautiful purple flower buds, which I will be sure to post on the blog when they arrive. The question I want answered is..... are they edible? I've looked up several blog sites, many people have eaten them without incident (after all they are beans), but the colour is alarming. Having said that, my Vitelotte potatoes were an alarming purple colour and they didn't kill me !!... Does anyone know if they are edible?