Don't use colored chalk. I KNOW personally that the blue chalk doesn't come out and others have mentioned they have had problems with red and green. I have always used the Purple be gone but you got to quilt it quickly because it use to vanish in less than 24 hours. I even had a client iron a top with the blue be gone markings and was amazed when I soaked the top overnight with a product called Linen Wash and the blue was actually removed. It is important to always do a test before proceeding.