ADD 3/4 cup boiling water to blue gelatin mix; stir 2 min. until completely dissolved. Add 1/2 cup ice cubes; stir until melted. Pour into crust; refrigerate 5 to 10 min. or until set but not firm.
MEANWHILE, repeat to dissolve red gelatin mix in separate bowl; stir in remaining ice cubes. Cool 5 min. or until slightly thickened.
SPREAD COOL WHIP over blue gelatin layer; cover with red gelatin. Refrigerate 2 hours or until set.