I mark my quilts when I am ready to do the quilting with a regular school #2 pencil. After I get the quilting done,
I bind it. I then put is in washer on gentile with laundry soap and a little Zeab stain remover (get at walmart in paint department). This takes all pencil marks out and never has did anything to my quilts. I started using it to get the stains out of my husbands work clothes years ago. This stuff takes the stains out and never harms the color.
Best stuff I have ever used.