I attended a class just last Saturday that was all about using colored pencils and other markers in quilts. The instructor encouraged the use of watercolor pencils, regular colored pencils, fabric paints, and anything else that would enhance your quilt. The main thing is to do a test to be sure it won't wash out or bleed. And always check with the manufacturer regarding how to make the color washable. Some use heat, others dont. Stay away from Sharpies tho--they look nice but bleed later.