I am sorry to tell you that there have been MANY posts on this site regarding the inability for color chalk to come off a finished quilt. I have a quilt that the blue Clover chalk still has not come off. You might want to see what some of the other posts have suggested by doing an advance search. They do tell you in the instruction to test it on a sample piece of fabric. I NEVER had any problems with Clover's white chalk. Good Luck !!