Reserve cocoa packet from cake mix. In a large bowl, combine cake mix, sour cream, eggs, milk and oil; beat on low speed for 30 seconds. Beat on medium for 2 minutes. Transfer half of the batter to a small bowl; tint orange with food colouring. To other half of batter, stir in contents of cocoa packet.
Divide chocolate batter among prepared cups. Carefully top with orange batter; do not swirl. Bake and cool as package directs.
To serve, top cupcakes with whipped topping and candy corn. Refrigerate leftovers.