Chromatella, Aurora, Gold Medal and Souix are hardies that have mottled pads. Chromatella's are quite pretty actually. Sunrise has slightly mottled pads but they turn solid green as the pad ages. Mexicana has what I call spotted pads, it is semi-hardy. May or may not survive your winter.
I have never tried a tropical because I don't think they would do well here. Too much change in water temp from day to night and the growing season would be too short. However, I'm going to get one next spring and give it a try and see what happens.
Here is a pic of chromatella where you can see the pads.
![](http://img.photobucket.com/albums/v56/SASHABEAR/Water%20Lilies/Water%20Lilies%202006/Chromatells06-18.jpg)
![](http://img.photobucket.com/albums/v56/SASHABEAR/Water%20Lilies/Chrom1.jpg)
This is Aurora
![](http://img.photobucket.com/albums/v56/SASHABEAR/Water%20Lilies/Souix07-21.jpg)