The subtropical, tender Taiwanese native Tricyrtis lasiocarpa, and it's hybrid offspring Tapei Silk (the latter of which I showed a few days ago), have that lovely amethyst blue color in the flowers that is so gorgeous in the clear fall light. Lasiocarpa is rated at zone 7 by most, and the winter hardiness of Tapei silk for me is still up in the air, but here's a proven survivor that has a touch of blue: this is the well-known Tricyrtis Togen (also spelled Tojen). I believe it gets its slight bluish tint from Tricyrtis formosana, not lasiocarpa; now formosana is only slightly hardier than lasiocarpa, and formosana hybrids overall are about 50-50 in surviving our Iowa winters, but Togen is totally rock hardy. It has large, lovely unspotted flowers that are orchid shading to white in the centers, with a yellow throat. The foliage is also striking in that the leaves are very large for a tricyrtis, and they are less prone to be damaged from hot summer weather (its heat tolerance probably comes from formosana). I could easily be convinced that Togen is one of the best, if not the very best, garden toadies.