In a small pot on medium heat dissolve sugar in water. Raise the heat, add the lime rind and bring to a boil. Lower the heat to a simmer and cook until slightly reduced. Remove from heat and discard the lime rinds. Stir in the food coloring and cool.
Fill 4 glasses with ice and distribute the lime syrup and lime juice, to taste, into each glass. Top with seltzer and stir. Garnish with lime slices.
Recipe courtesy of Sunny Anderson, 2008