Prepare Roll-Out Cookie recipe. Prepare Color Flow Icing Mix according to package directions. Cut out and bake tree cookies. Cool.
Divide icing and tint green, yellow, blue, orange, red and violet. Using tip 3 and full-strength green icing, outline tree. Thin icing with a small amount of water and cover tree. Let set overnight. Using tip 3 and yellow icing, pipe zigzag line on tree. Using tip 3 and red/violet/blue/orange icings, pipe dot ornaments on tree. Let set.