Brightly colored juices float on top of grenadine, a red fruit-based simple syrup, giving the cocktail a beautiful visual effect.
Pour orange juice, tequila, and lemon juice into a large pitcher. Tip pitcher at a slight angle, and carefully pour grenadine down side.
Divide mixture among 8 ice-filled glasses, and top off each with club soda. Stir, garnish each with zest, and serve immediately.