You can ice these with royal icing and top with whatever you want or you can go this route more decadent route and smear some frosting on them, then sprinkle some pretty rock candy for a bit of bling.
At least one day in advance, dye the rock candy crystals. Lay out a sheet of parchment paper on a baking tray. Assemble 4 metal or glass bowls, and pour 3oz of vodka into each. Add food coloring to each bowl, getting progressively darker, and stir thoroughly. Divide the rock candy into roughly (4) 1/2lb groups. Dye one shade at a time, by putting handfuls of rock candy into the strainer, dipping into the bowl, lifting the strainer to drain, and spreading out the rock candy into a single layer on the baking sheet. Repeat for the other 3 shades, placing a thin piece of parchment between colors on the baking sheet. Place in the (cool) oven to dry overnight undisturbed. Preheat the oven to 350º. Roll out the sugar cookie dough onto a floured piece of wax paper, into a large rectangle, about ¼” thick. Flip onto ungreased baking sheet. Bake for 12-15 minutes, until golden brown. Use the cookie cutters to cut out cookie shapes and move to a wire rack to cool. Combine all the ingredients for frosting in a mixing bowl and beat for 1-2 mins. Place a sheet of tin foil underneath the wire rack of cookies, and use a spoon to spread an even glaze of frosting on each cookie. Sprinkle on rock candy and let set. Adapted from Sugar Britches Cakery