Reading Jane Perrone's excellent U.K. garden blog reminded me about gardener/author Karen Platt and her knowledge of purple/black plants. Jane recently conducted a Q&A with Karen that you can read here.
Karen occasionally appears on HGTV's Gardening By the Yard to discuss and display unusual plants of unusual color. Her website can be found here.
And I've just added her wonderful-looking book Black Magic and Purple Passion to my Amazon wishlist...hint, hint, friends and relatives!