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.