1. In a small bowl, sift together flour, baking powder, baking soda and salt. 2. In a separate bowl, whisk eggs and sugar until creamy. Add vegetable oil and whisk. 3. Add lemon juice and zest and mix. 4. Alternating with your dry ingredients and buttermilk, add slowly to wet ingredients. 5. Carefully fold in blueberries. 6. Fill lined muffin pan with cupcake batter, about 2/3 of the way. Bake 15-17 minutes. 7. Allow to cool before topping with buttercream frosting. 8. To make the frosting, beat together butter, icing sugar and milk using an electric mixer.  9. Once the ingredients are well-mixed and smooth, add gel food coloring of each color and beat until tinted. 10. Scoop into a large piping bag with Wilton’s 1M icing tip attached. Frost each cupcake. 11. Top off each cupcake with one blueberry and serve.