I've had the blue water soluble show back up also. And please do not use colored chalk, I've have several things w/chalk marks on them that won't come out! I have been very pleased w/the Crayola markers, no problems w/them at all so far. I have used the Roxanne pencils and they didn't wash out either. I have used school chalk but I guess I should try a different brand because mine always breaks w/in a few minutes of starting to draw.
And for my oops...I once used a Vis-A-Vis pen on a quilt thinking it would wash out since it is a water washable pen, but that only works on plastic not fabric. Thankfully the pen color sort of blended in w/the quilt fabric so not really noticeable.