I feel for you. I finished a double wedding ring quilt recently and had a deep burgundy fabric in it. I tested just that fabric before I washed the quilt and it faded bad. In doing research I found a woman who used dawn platinum dish detergent and soaked her quilt for 12 hours. I put mine in the washing machine used probably 1/4 cup of detergent and cold water. Let the quilt sit overnight. It did fade some from front to the white muslin back around some machine stitching places. I think what happens is that the color fades into the water overnight and so there isn't much to fade into the surrounding material. It salvaged my quilt, but from now on I will test all dark colors ( as I had a piece ruined by a turquoise piece) and get rid of the fabric if it fades. Sorry.