Mark-B-Gone marking pen is blue for marking light fabrics and also includes a white pen for marking dark fabrics with its water soluble ink.
Use marking pen on washable fabrics to transfer pattern markings and quilt or craft designs. Some fiber contents, fabric finishes or dyes (red and pink in particular) may not be suitable for use with this pen. To remove marks, rub gently with clean damp cloth well moistened with plain water. Not recommended for dry clean only fabrics.
Always test any marker on a small piece of fabric before using. Some sizings may prevent the marks from washing out.