1. With an electric mixer on medium-high speed, beat butter and cream cheese until fluffy, 2 to 3 minutes. Reduce speed to low. Add sugar, 1/2 cup at a time, and then vanilla, and mix until smooth and combined, scraping down sides of bowl as needed. If not using immediately, frosting can be refrigerated up to 3 days in an airtight container; before using, bring to room temperature, and beat on low speed until smooth again.

2. Place food coloring in a resealable plastic bag. Add coconut flakes. Shake bag to evenly coat coconut with food coloring. Use immediately.

3. Using a serrated knife, trim top of coconut cake to make level. Place coconut cake, trimmed side up, on a cake turntable or serving plate, and spread with about 2 cups frosting. Top with banana cake. Using an offset spatula, spread remaining frosting over entire cake. Sprinkle the top and sides with coconut. Cake can be kept refrigerated, covered with a cake dome, for up to 3 days.