Royal icing takes at least 8 hours to dry so you will want to start your projects at least 1 day before serving.
Make cookies. Prepare and roll out dough following recipe directions. Use snowflake cutter to cut out shapes. Bake and cool cookies.
Decorate light center cookies. Prepare Royal icing according to instructions. Divide icing into four portions. Tint four shades of blue from light to dark. Reserve some full-strength icing in darkest shade. Thin remaining icings, separately, according to package directions. Use tip 3, a cut parchment bag and full-strength dark blue icing to outline cookies. Use tip 3, a cut parchment bag, and thinned icing in darkest shade to pipe an outline next to first outline. Repeat with thinned icing in second darkest shade, second lightest shade and lightest shade of icing. Immediately use a toothpick to drag icing from snowflake arms toward center of cookie. Let cookies dry overnight. Reserve remaining icing.
Decorate dark center cookies. You will outline cookies as for light center cookies, but you will add a second group of outlines from darkest to lightest to create the darker center design. After completing the lightest outline in the first group, start the second group with darkest thinned icing next to the lightest outline. When both groups are complete, immediately use toothpick to drag icing from snowflake arms toward center of cookie. Let cookies dry overnight.