Use food coloring gel in a squeeze bottle or a food-safe paintbrush to make lines in the piping bag. Once meringues are cooled, store them in an airtight container at room temperature.
Preheat oven to 200°. Let egg whites stand 20 minutes. Beat egg whites at high speed with an electric mixer, using whisk attachment, until stiff peaks form. Reduce speed to medium. Add vinegar; add sugar, 1/2 cup at a time, and beat until blended. Beat 2 minutes. Beat in extract.
Paint 3 or 4 evenly spaced thin stripes of red food coloring gel on inside of a decorating bag, starting at tip and ending three-fourths of the way up bag. Gently spoon meringue into center of bag, filling three-fourths full. Snip end of bag. Pipe about 2 Tbsp. meringue onto 1 parchment paper-lined baking sheet, leaving 1 inch between each cookie. Repeat with remaining meringue, using a clean bag for each batch.
Bake at 200° for 2 hours. Turn off oven, and let meringues stand in oven until completely cool (about 3 hours).
Melt milk chocolate morsels in microwave according to package directions. Stir until smooth. Dip bottom of each cooled cookie in melted chocolate, and place on a parchment paper-lined baking sheet. Let stand 15 minutes or until chocolate sets.