Heat oven to 350 degrees. Using shortening or butter, grease 12-cup Bundt pan. (Do not use cooking spray.) Mix together box cake mix, pudding, eggs, vegetable oil, water and sour cream. Pour half of the batter into a medium bowl. Divide the other half of batter equally between 2 small bowls. (About one cup each.) Add enough red food coloring to one of the small bowls to achieve bright red color. Mix well. Add enough green food coloring to the second small bowl to achieve bright green color and mix well. Pour half of the white batter from medium bowl into Bundt pan. Spoon red batter over white batter in Bundt pan without mixing the two colors together. Carefully pour green batter over red batter without mixing the red and green colors. Pour remaining white batter from medium bowl over the top. Bake for about 35 minutes or as directed on box, and when toothpick comes up clean. Let cake cool (about 30 minutes.) Turn cake upside down on serving plate. Divide frosting between 2 small microwavable bowls. Microwave 1 bowl for about 10-12 seconds. Mix well with spoon until smooth enough to drizzle. With the spoon, drizzle white frosting over the cake. Microwave second bowl of frosting; stir in green food color. Mix with spoon and drizzle over cake. Immediately sprinkle with decorative sugars before green frosting hardens. Let frosting firm then cut and serve. Makes one large Bundt cake or 6 mini Bundt cakes.
Jan's Note: For mini Bundt cakes, I place my cake batter in three separate piping bags; one for the white, red and green. It's easier to pipe the colors in layers!