Prepare lime, orange and 1 package strawberry gelatin separately as directed on package, using 1 cup boiling water and 1/2 cup cold water for each. Pour each flavor gelatin into separate 8-inch square pan sprayed with cooking spray. Refrigerate 4 hours or until firm.
Add remaining boiling water to remaining dry strawberry gelatin mix in large bowl; stir 2 min. until completely dissolved. Stir in remaining cold water. Refrigerate 45 min. or until slightly thickened.
Cut gelatin in each square pan into 1/2-inch cubes. Add 1-1/2 cups of each flavor gelatin to thickened strawberry gelatin in bowl along with half the COOL WHIP; stir gently until blended. Pour into 9x5-inch loaf pan sprayed with cooking spray. Refrigerate 4 hours or until firm. Meanwhile, refrigerate remaining gelatin cubes and COOL WHIP until ready to use.
Unmold dessert onto plate; top with remaining COOL WHIP.