These are beautiful! I've used the Pentel fabric crayons and they work well too and in the same way you describe. I've coloured in after quilting, you can do both ways. It's a good technique on a landscape quilt as well, if you don't have a fabric the exact colour you want or to apply shading or blur edges between pieces. Your snowmen are 'snow' cute and I LOVE the multicoloured sashing squares! :-D