1. Heat oven to 350 degrees F. Coat 15 x 10-1/2 x 1-inch jelly-roll pan with cooking spray. Line bottom with waxed paper; coat paper with spray.
2. Combine cake mix and flour in bowl. Prepare following package directions, using egg whites, water and oil. Scrape into prepared pan.
3. Bake in 350 degrees F oven 30 to 32 minutes, until golden and cake springs back when touched. Cool in pan on rack. Invert; remove paper.
4. Beat mousse and milk in bowl. Add peanut butter; beat until smooth and slightly thickened, 4 minutes. Tint lightly with coloring. Chill. Melt jelly in small saucepan over low heat or in glass bowl in microwave oven.
5. Cut cake lengthwise in half, and then crosswise into half, making total of 4 pieces. Slice each piece in half horizontally. Spread jam on noncut sides of 4 bottom pieces. Spread mousse over other 4 pieces. Invert jelly layers onto mousse layers, so rough, cut side is facing up. Refrigerate 20 minutes. Cut each sandwich diagonally into quarters.