Line 8-inch square pan with foil, with ends of foil extending over sides. Microwave white chocolate and milk in microwaveable bowl on HIGH 1 to 2 min. or until chocolate is almost melted; stir until completely melted. Stir in food colorings until well blended.
Spread half the white chocolate mixture onto bottom of prepared pan; sprinkle with chopped chocolate bars. Immediately top with remaining white chocolate mixture and sprinkles. Refrigerate 2 hours or until firm.