1. Remove ends from lemons and discard. Remove lemon peel with a knife; set aside. Quarter lemons; squeeze juice into a bowl. Remove and discard white membrane.
2. Place the peel and pulp in a blender; cover and process until coarsely chopped. Add peel mixture and sugar to lemon juice; mix well. Let stand for 30 minutes.
3. Stir in milk. Strain lemon mixture; add club soda and food coloring if desired. Serve immediately in sugar-rimmed glasses if desired. Yield: 8 servings.