Pulse graham crackers in a food processor to make crumbs. Add melted butter and sugar and process until crust mixture can be pressed firmly and maintain its shape. Press an even amount of crust over the bottom and slightly up the sides of a 24-cup muffin tin.
Mix lime-flavored gelatin and unflavored gelatin together in a bowl. Add boiling water and stir until gelatin is dissolved. Add vodka; stir in enough heavy cream to achieve desired color. Fill prepared muffin cups to the top with the gelatin mixture. Cover with plastic wrap and refrigerate until set, at least 4 hours.