Heat oven to 200 degrees. Place egg whites, sugar, and cream of tartar in a bowl of your stand mixer. Place bowl over boiling water on the stove. Whisk vigorously until sugar dissolved and there are no more sugar granules visible. Remove from heat and whisk in extract.
4 egg whites at room temp
Using the whisk attachment on stand mixer, mix on medium high until egg whites become bright white but still runny. Add in food coloring to the color you want and continue to beat to form stiff peaks.
4 egg whites at room temp
Place mixture into piping bag with large star tip. Pipe cookies onto baking sheet lined with parchment paper or silicone mat. Make cookies about 1 inch in width, 2 inches high and place 1 inch apart on baking sheet. Sprinkle with the multi color sprinkles.
4 egg whites at room temp
Cook for 2 hours. After 2 hours, turn off oven, open door slightly and let sit in oven an additional 2 hours.
4 egg whites at room temp
Place the star sprinkles on top with a tiny dab of frosting. Serve and enjoy!