Fons and Porter , Sew Easy, and Bohin all have the same mechanical pencil available. Instead of pencil lead the "leads" are colored ceramic. They mark just as easy as any pencil, the line is very thin to your thread will cover most of the line and the markings can be erased with a white pencil eraser or washed away quite easily.
I use the Bohin (it's cheaper than the others) exclusively for marking my quilt tops.