01 - Preheat the oven to 200°F. Line two baking sheets with parchment paper.
02 - In a grease-free mixing bowl, combine egg whites and cream of tartar. Using an electric mixer, beat at medium speed until soft peaks form.
03 - Add granulated sugar a tablespoon at a time, beating on high speed until the mixture becomes stiff and glossy, about 5 to 7 minutes.
04 - Incorporate salt and vanilla extract, mixing briefly to combine.
05 - Fit a piping bag with a large star tip or round tip. Using a food-safe brush, paint one stripe of red gel food coloring and one stripe of blue, leaving a plain section for white.
06 - Transfer the meringue mixture into the prepared piping bag, trying not to disturb the colored stripes. Pipe 1 to 1 1/2-inch wide mounds onto the lined sheets, spacing them about 1 inch apart.
07 - Bake for 1 hour and 15 minutes or until the kisses are dry and crisp. Turn off the oven and let the meringues cool inside with the oven door closed for an additional hour.
08 - Carefully peel meringues off the parchment and store them in an airtight container at room temperature for up to five days.