Add 1-1/4 cups boiling water to orange gelatin mixes in medium bowl; stir 2 min. until completely dissolved.
Pour into 8-inch square pan sprayed with cooking spray. Repeat with remaining boiling water and grape gelatin mixes. Refrigerate 3 hours or until firm.
Meanwhile, melt chocolate as directed on package; cool slightly.
Pour into small resealable plastic bag; seal bag.
Cut small piece off one bottom corner of bag; use to squeeze chocolate onto waxed-paper covered baking sheets to make 12 spider webs or other Halloween shapes. Refrigerate until chocolate is firm.
Cut gelatin in each pan into 1/2-inch cubes.
Layer orange gelatin cubes, half the COOL WHIP and grape gelatin cubes in 12 (6-oz.) plastic cups. Refrigerate until ready to serve.
Top parfaits with remaining COOL WHIP and chocolate decorations just before serving.
