This has happen to me!! I googled "brown marks on quilt". I got instructions for washing the quilt in a Mixture of white vinegar and water. I have forgotten the exact mix but I think I used at least two gallons to a washer full of water. IT WORKED!, I thought the quilt was ruined so I went for it!! I was amazed. My mistake??? I washed with soap and oxyclean. It caused a chemical reaction with the blue marker. Now I soak in water til marks are gone. Then I wash with soap. No oxyclean. I was saved. Hope you are too!