A lot of camellias are vegatatively hardy in zone 6. The problem is often how well the flower buds resist the cold. The trick is to find a fall-bloomer that blooms soon enough so that you have a chance to enjoy the blooms before damaging cold sets in. What helps the blooming process, I believe, is to find a variety that can take the sun. I believe the sun encourages the flowers to open sooner.
One fall-blooming variety that will take full sun, at least for me, is Autumn Pink Icicle. It is a hybrid between C. japonica, C. oleifera, and C. saluenensis. I have had mine planted in full sun for well over a decade. This year it started blooming in early October. When the temperatures start dropping into the low twenties and teens repeatedly, it will shut down and the rest of the flower buds will not open unless the cold event is brief and it is followed by extended periods of more moderate temperatures.
My best performance with this one was the winter of 2012-2013 when it continued to bloom until late January. It was great!
Here's a recent picture taken on Oct 6th
Here it is on Election Day with butterfly