Preheat your oven to 350 degrees.

Lightly grease or line a 9x13 baking dish.

In a medium mixing bowl combine your cake mix, water, oil and eggs.

Stir until well combined.

Add your green food coloring until you get your desired green shade.

Pour the cake batter into the baking dish.

Bake the cake for 30-35 minutes until a toothpick inserted comes out clean.

Set the cake aside to cool.

Using the handle of a wooden spoon poke holes all into the cake.

In a medium bowl combine the instant pudding and milk.

Whisk until smooth.

Add your red food coloring until you get the red color you like.

Carefully spoon or use a clean cooking syringe to insert the pudding into the holes.

In a large bowl using an electric mixer whip up the softened butter.

Add the powdered sugar to the butter and continue to beat until creamy and fluffy.

Add green food coloring until the desired Grinch Green color.

Frost the cake with the buttercream.

Top with green sprinkles and heart sprinkles.

Set the cake in the fridge to chill for 2 hours.

Slice and serve!