1Heat oven to 350°F. Spray 6-count nonstick muffin top pan with cooking spray. Make cake mix as directed on box, using water, oil and egg whites.
2Divide batter evenly among 3 medium bowls. Stir melted chocolate into 1 bowl. Stir yellow food color into second bowl. Stir orange food color into third bowl. Starting with chocolate batter, dollop 1 tablespoon of each color batter into each muffin top cup. (Cover and refrigerate remaining batter until ready to bake; cool pan 15 minutes before reusing.)
3Bake 10 to 12 minutes or until golden brown around edges. Cool 5 minutes; remove from pan to cooling rack. Cool completely. Repeat with remaining batter to make additional 12 muffin tops.