20 Grayscale Kids Coloring Book Simply put, it is an easy and amazing way to add professional shading to your coloring, without having to add the shade yourself! Grayscale coloring books are a bit different from the typical coloring book that use line drawings. These images capture shading and values of grays for you to use as a guide for dark and light. Suitable mediums to use are copic markers and other alcohol based markers, other water based markers, gel pens, colored pencil, pastels and more.