I used DMC floss years ago and remember some problems with bleeding on dish towels, I don't remember what I did with them. Last year I wanted to embroider some Christmas dish towels and instead of using my old DMC stash, I switched to Finca (Prencia) Perle #8 for some bluework. I used the water eraseable blue marker. When I rinsed the towel under water the dark blue did not bleed. I like this floss much better than DMC, as it does not fray like DMC. I have also have the same thread in #12, which is a finer thread than the #8. I have also "discovered" a Pilot FriXion ball marker that is removed with heat. I tried a sample and when I ironed the sample, the mark was gone. I also tried the marker with a crayon color and the mark still disappeared. I know that does not help your problem when you have put a lot of time and effort into a project. I will certainly watch for any answers that may resolve your problem.