I made some blackberry wine and spilled some. I wiped it up with a towel, and it is now very stained. So I wondered if I could use the spent blackberries after wine making to make dye. I had always just fed them to the critters. So I used information from this site to make a dye. Basically you just simmer then berries and strain them. You pretreated the yarn with alum. Then you add the pretreated yarn to the dye, simmer it and then let it cool in the pot overnight. Here is the dyepot with the yarn in it.
Then you wash and rinse the yarn and let it dry. Here is the yarn after drying, photographed in room lighting.
And here it is in the sunlight (where I think you can see the color a little better).
And here are the hogs still getting to eat the leftover blackberries.