I think that blue is a recesesive trait, so you are only going to get it if it's passed by both parents. So the red Norton could carry it if it has blue ancestors, but in that case you'd only expect half the offspring to be blue.
I'm wondering about the 'hybrid' bit too. I've seen Norton violacea's listed as hybrids, but as far as I'm aware they are pure violacea, though I'm not sure if they are a mixture of strains/subspecies. Anyone know more?