Tint frosting with black and blue food colors to make desired gray color. Using serrated knife, cut rounded top off cake to level surface; place cake cut side down. <a href="/PDF/RecipeTemplates/Robot_Cake_template.pdf" target="_blank">Cut cake as shown in template</a>. On tray, arrange cake pieces as shown in template, attaching to tray with small amount of frosting. To "crumb-coat" cake, spread thin layer of frosting over top and sides to seal in crumbs. Refrigerate or freeze cake 30 to 60 minutes.