Prepare and roll out cookie dough. Cut using cutter; separate halves of heart. Bake and cool cookies.
Use tip 2 to outline one heart section in full-strength dark rose Color Flow icing and the other in full-strength light rose Color Flow icing. Flow in with thinned Color Flow icing in matching colors. Let dry.
Use tip 2 and full-strength dark rose and light rose Color Flow icings, pipe message on cookies in opposite colors. Let dry.