To make the lemonade pink, we added cranberry juice (or you could substitute pomegranate juice, if you prefer).
Pour lemon juice through a fine mesh sieve into a large serving container; add sugar, and stir until sugar is dissolved. Stir in 3 quarts cold water and the cranberry juice. Refrigerate until ready to serve, up to 1 day. To serve, add ice cubes to fill and garnish with lemon slices.