In a small saucepan over medium heat, combine the sugar and 1 cup water, stirring until the sugar fully dissolves and the liquid runs clear, about 3 minutes.

Remove the syrup from the heat and let it cool to room temperature, about 20 minutes.

In a large pitcher, combine the cooled syrup, fresh lemon juice and the 4 cups cold water, stirring to combine.

Add the green food coloring one drop at a time, stirring between drops, until the lemonade reaches a bright grass-green.

Refrigerate the base until cold, at least 1 hour, or make it up to 2 days ahead.

Just before serving, top with the chilled club soda and stir once, gently, so the bubbles hold.

Pour over ice and garnish each glass with a lemon wheel on the rim.