In medium-size bowl, whisk together confectioners sugar, milk, lemon rind, lemon juice and salt until good glazing consistency. Reserve 2 tablespoons. Frost tops of cookies with the remaining glaze, leaving the edges of the cookies unfrosted. Add food coloring to the reserved glaze. Stir in a few drops of milk for a good drizzling consistency. Dip a fork into thinned glaze and drizzle over the frosted cookies.