Place paper cupcake liners in each of 24 regular-sized muffin cups.
Prepare white cake mix according to package instructions.
Divide batter evenly among 3 bowls.
Using the food coloring, color one bowl of batter a darker green, one bowl a lighter/medium green, and leave one bowl plain white. You could actually make the final layer an even lighter shade of green if you prefer, but I wanted a starker contrast between the cupcake and the green frosting on top, so I left it plain!
Divide the darker green batter evenly among muffin cups, about 2 tbsp. of batter, or 1 scoop with a standard cookie scoop. Tap the pan on the counter to evenly spread and distribute the batter.
Divide the lighter/medium green batter evenly among muffin cups, using the same method.
Repeat with plain white batter.
Bake cupcakes at 350 degrees for 16-18 minutes, or until the edges of the cupcakes are golden brown.
Cool in pan on wire racks for about 10 minutes, then remove cupcakes from pan, and cool completely.