Bake cake in a 9x13-inch pan according to package directions. Allow to cool slightly.
Using the handle of a wooden spoon, poke holes all over the cake, about 1 inch apart.
In a bowl, whisk together pudding mixes with cold milk until smooth. If desired, divide pudding into bowls and tint with pastel food coloring.
Pour pudding evenly over cake, letting it fill the holes.
Spread whipped topping over the cake to cover completely.
Sprinkle with green-tinted coconut to resemble grass. Decorate with Easter candy and Peeps.
Chill cake for at least 2 hours before serving to allow pudding to set.