Love your cute design and fabulous quilting. I did this years ago using "water color pencils" and clear Aloe Vera gel from Walmart to set it. The gel moistens the pencil, but because of its consistency, it doesn't allow it to bleed further into the fabric. I can't remember the name of the author of the book I bought that used that technique, sorry. Also not sure if it would be colorfast if washed, but could certainly be used for a wall hanging, if you want to try it.