Originally Posted by greensleeves
I'm using Fons and Porter Mechanical Fabric Pencil(red/white pen with white "lead") to mark on a dark background fabric and it does come off with damp cloth or in laundry. Don't know if it would work for you, I got mine 40% off at Hobby Lobby and it comes with a package of refills. Refills can also be ordered from Connecting Threads.
I used these to mark fabric that I was quilting for a jacket. What I liked about it was even though it'd wear off when the light from the machine hit it it would glow so you could still see the line.