I have 6 of these growing along a fence in Massachusetts and we've had a couple of hard winters since I planted them so I think they are hardy to Zone 5 - not sure 5a or 5b. Mine did beautifully until this recent hard winter when most were de-barked by rabbits. I'm going to do a lot of pruning but may have to replace one or two that were pretty devastated. Live and learn for me - this would have been our 4th summer with them and I was really looking forward to them especially after a great season last year, but I think it will be a while until we get another show like last year now. We've always had the bunnies and there was no problem in past years, but now I know better.

As far as color, technically they are a pale yellow but in our garden they are so pale I really think of them as white/cream. They may vary slightly based on soil and climate? We did have a small branch of very pretty pale pink (and I don't usually like pink much), a sport, I guess, but that may also have been lost to the killer bunnies.