Prepare royal icing following recipe instructions. Combine Royal Blue and Kelly Green icing colors to get blue color shown. Combine Leaf Green and Lemon Yellow icing colors to get green color shown. Tint 1 cup icing each blue and green using color combinations provided. Using Golden Yellow, Orange and Red-Red icing colors, tint 1 cup icing each yellow, orange and red. Reserve remaining icing white.
Prepare six decorating bags with tip 3. Fill separately with full-strength blue, green, yellow, orange, red and white royal icing; outline cookies. Reserve ½ cup white icing full-strength for later step. Thin remaining white and colored icing to count of 10; flow in. Let cookies dry 8 to 10 hours or overnight.