Incense, caerulea and incarnata are all hardy in Z8. Anectdotal stories have Amethyst as hardy except in harsher winters. Lutea, affinis and tenuiloba are hardy, but since they have small flowers, they're rarely available commercially. With its incarnata parentage, Lady Margaret may be hardy in Z8 as well. I've got some cuttings going, and spring year plan to plant one in a sheltered spot to get it established by the time winter rolls around. So ask me again in 18 months and I might have additional news for you.

There's a scattering of others as well, but those will get you started.