Puree the diced mango in a food processor until smooth and fold in the white cake mix until well combined. Be careful not to overmix so your cakes bake flat.
Divide the batter evenly between 3 bowls and color the 1st bowl a light pink, the 2nd bowl slightly darker, and the 3rd bowl the darkest shade of pink*.
Pour batter into greased and lined 8" cake tins and bake at 350 degrees for 25-30 minutes or until a toothpick inserted into the center comes out clean.
Allow the cakes to cool in their pans for 10 minutes before turning out onto a wire rack. Let cakes cool completely before frosting.
To make the frosting beat the coconut oil and vanilla until fluffy and add the powdered sugar a 1/2 cup at a time until you reach your desired consistency. If your frosting gets too thick you can add unsweetened almond or coconut milk 1/2 Tbs at a time until you reach a spreadable consistency.
To decorate lay your darkest layer on your cake stand and add 1 cup of frosting, smoothing it into an even layer with an offset spatula. Top it with the medium shade and repeat. Top with the lightest shade and crumb coat your cake with a thin layer of buttercream. Refrigerate for 15 minutes or until buttercream is no longer tacky.
Frost your cake with a final, even layer of buttercream smoothing the top and sides with a large offset spatula or cake scraper.
Decorate the top with red M&Ms or leftover frosting.
Be sure to refrigerate the cake before serving so the frosting doesn't get too soft.
*To get a nice deep shade of pink I added a tiny bit of red to the darkest layer along with the pink you can omit this and just use pink if it's all you have.**The calories shown are based on the cake being cut into 10 pieces, with 1 serving being 1 slice of frosted cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.