I know better than to heat set any washable marker- be it a Crayola one or one specifically made for marking quilt tops. I used the lightest colors- peach, yellow, and a light green. I think with any marker- even the ones made for quilts(which I have)- it is a good idea to test to make sure it will wash out. I have one quilt that still has the marks from a washable marker that was pretty darn permanent.