Preheat oven to 350. Line a jelly roll pan with aluminum foil, extending foil 1" over ends of pan. Prepare cake mix according to package directions. Spread batter evenly into prepared pan. Bake for 30 minutes. Immediately turn onto towel sprinkled with powdered sugar. Peel off foil and begin rolling at narrow end, roll up cake with towel, jelly-roll fashion. Cool thoroughly. Meanwhile, in a mixing bowl, combine sweetened condensed milk, lemon juice, lemon peel, and food coloring. Mix well. Fold in whipped topping. Unroll cake; trim edges. Spread half lemon mixture; reroll without towel. Place on serving platter, seam side down. Spread remaining mixture over roll.