Preheat oven to 350 degrees for metal and glass pan(s), 325 degrees for dark or coated pan(s). Use baking cups for cupcakes. Will need 18 to 20 baking cups.
Blend cake mix, water, oil and egg whites in a large bowl at low speed until moistened (about 30 seconds)
Beat at medium speed for 2 minutes. Divide batter. Place one cup of batter into 3 separate small bowls, saving one cup batter for white. Tint one bowl with 4 drops fushia gel food coloring, one bowl with 4 drops teal gel food coloring and one bowl with 4 drops sunny yellow gel food coloring. Leave one bowl white. Stir food coloring into batter until you reach the desired color.
Starting with one colored batter, place a small spoonful of batter into each baking cup liner, continue with remaining batter using a small spoon and alternating colors as you go until all batter is gone.
Bake in oven for 18 to 21 minutes. Cupcakes are done when toothpick inserted in center comes out clean.
Remove cupcakes for pan and cool completely before frosting.
Add 2 drops of gel food coloring per container of frosting. Stir until well combined. Frost cupcakes using a decorating tip of choice and piping bag or simply frost with a knife.