1In blender, place tequila, liqueur, lime juice, 1/2 cup simple syrup, the green food color, yellow food color and ice cubes. Cover; blend on high speed until smooth.
2Place 2 teaspoons simple syrup on small flat plate. Place coarse sugar on another small flat plate. Dip rims of 5 margarita glasses in simple syrup and then in coarse sugar. Divide margarita slush evenly among sugar-rimmed glasses. Garnish with orange slices. Serve immediately.