I have heard people say there are some colors of the Crayola markers that don't wash out as well as others.
I used the one with the light pink cap to mark a queen size triple Irish chain in the plain squares. It took me at least a couple of weeks, and probably closer to three weeks, from the time I first started until the binding was done. I washed the quilt in hot water. The marker came out and the quilt is fine. Since that quilt was a 12 year old UFO I think the fabrics were probably pre-washed. The batting is a Quilter's Dream select weight and it wasn't pre-shrunk.