Combine sugar and 1/3 cup water in a
small saucepan. Cook over high heat until
simmering; stir until sugar is completely
dissolved, about 2 minutes. Cool.
Combine cooled sugar syrup (should be
1/3 cup), lime juice, lemon juice and
jalapeño in a blender. Blend on highest
speed until pureed, about 1 minute. Pour
into a pitcher.
Add tequila and triple sec to pitcher.
Refrigerate until serving. To serve, run a
lime wedge around rims of 6 glasses. Dip
glass rims in white or green decorating
sugar and fill glasses with ice. Pour
margaritas over ice and serve.