Mix cake mix, butter, vanilla, and milk together on a stand mixer using the paddle attachment. Mix until ingredients are brought together like cookie dough, approximately 2 minutes on 2nd speed on a 3-speed mixer. Sheet or roll dough approximately ¼ inch thick. Cut our desired shapes of cookies, placing cut our shapes on a parchment lined pan. Bake at 350F until golden brown. Let cookies cool completely.
Pipe a ring of royal icing around the exterior of each cookie. Heat blue, pink, red, and yellow flat icings at 100 to 110 degrees in microwave or boiler. Mute blue, pink, red, and yellow icings with white icings to desired color shade. Prepare piping bags of each colored icing. Pipe desired color icing in the center of each cookie and spread with a spatula knife to the outer white circular border. Top with edible flowers or other natural toppings, if desired.