I know of 'SnowQueen', 'Red Hot' and a tree variety.

I have a varigated variety of hibiscus and remember reading about it on the web but forget the name now .
I think it is hardy .
This hibiscus doesn't get a good flower.
The flower is burgandy and stays in the form of a bud .
I have to track down the name and read about it again , I love the foliage .
Here is a link to the one I have , It had some root trouble last year so I nursed it in a pot for the winter and it has paid off because now it is well rooted and growing very nicely once again .

http://www.davidbowie.com/users/7TowersSerendipity/hibivari.jpg

Here is a link that might be useful: {{gwi:885960}}