I've always used vinegar and it's worked every time. I even made a red and white quilt with JoAnn's Country Classic solids and I've machine washed it since I've finished it and there is not one single spot of red on the white. I just fill put the fabric in the washing machine, dump in half a gallon on white vinegar, fill the machine with cold water just to cover the fabric and let it sit for at least an hour. I then empty out the water, and wash with laundry soap on hot. I throw in a piece of white fabric just to be sure and I've never had a color transfer to the white. I'll probably get flak for this, but, just saying, it has worked for me for years.