STIR 1-1/4 cups of the boiling water into the dry orange gelatin in medium bowl at least 2 minutes until completely dissolved; pour into lightly greased 8-inch square pan. Repeat with remaining 1-1/4 cups boiling water and dry grape gelatin in separate bowl. Refrigerate at least 3 hours or until firm.
CUT gelatin in each pan into 1/2-inch cubes. Place 1/4 cup of the orange cubes in each plastic cup; cover each with 1 tablespoons of the whipped topping and 1/4 cup of the grape gelatin cubes. Top each with an additional 1 tablespoons of the remaining whipped topping.
MELT chocolate as directed on package; cool slightly. Pour into small resealable plastic bag; seal bag. Cut a small corner off of one of the bottom corners of bag; squeeze chocolate over whipped topping to resemble spider webs or other Halloween shapes. Add decorations as desired.