I had a fair amount of rust on 'A Tribute to Mary Gaskins' this past rainy winter. It was its first winter here; I don't know how it will perform in the future. (I still haven't seen bloom on it!
) You might want to take that into consideration.
In my experience, crossing something colored with something near white, lightens whatever color you started out with. I don't know if that generally holds true, though.