1. Trim the tops of the cakes to make them level. Stack the cakes on a cake stand, spreading a layer of buttercream between each with an offset spatula.

2. Cover the cake with a thin layer of flavored buttercream (this is the crumb coat), smoothing it with a bench scraper. Refrigerate until set, about 15 minutes. 

3. Divide remaining flavored buttercream among 4 or more bowls depending on the number of desired colors for the cake. Add food coloring to each bowl. Recipe Tip: Add a small drop of brown liquid gel food coloring or brown liquid food coloring to each buttercream color to achieve a classic, warm and muted palette that embodies the '60s aesthetic.

4. Transfer each color frosting to a separate piping bag fitted with a grass tip. 

5. Holding a piping bag perpendicular to the cake and working from the base of the cake, pipe a small section (pulling downward) of buttercream.

6. Continue piping small sections with the grass tips, alternating the colors, sizes and shapes of each area as desired or until there is no crumb coat showing. 

7. Once the sides are complete, cover the top of the cake with the piping technique as desired; alternating colors, shapes and sizes of frosting.

8. Refrigerate the cake at least 30 minutes to allow the frosting to set.

9. Add mini disco balls for a sparkly touch and to nail the groovy theme! - optional