"You can hear blue in wind over water and wherever flax blooms and when evening steps into lonely rooms. Cold is blue..." From Hailstones and Halibut Bones by Mary O'Neill.
I've been soaking a red cabbage in some rain water for about two weeks. On Sunday Jude inspired me to move on to the next step, fabric. I heated up the rain water and cabbage on the stove and tossed the fabric in. Simmered all of it for about an hour. Clockwise starting with the upper right hand corner: Cotton, a silk/rayon velvet, wool, and raw silk. It's all been washed and dried.
The brightest results came from the raw silk and silk/rayon velvet. I also tried over dyeing some cotton prints and a light blue hemp/cotton blend. The cottons didn't hold the color well. The hemp blend darkened enough to look like a different shade.
Even better, I did a second batch and then tossed in the washing machine with a load of laundry to rinse. I make my own laundry soap usually with washing soda, borax and grated soap. When I pulled the fabric out of the washing machine it was a bit more aqua than the first batch. I think the washing soda acted as a modifier to change the color of the dye a bit. I'll show pictures when I have natural light. Very hard to capture the difference with the lighting I have right now.