I tried to make another rainbow layer cake last week, and the last layers (green, blue and purple) came out very badly. So badly that I had to chuck them.
The flavours here are (from left to right):
It was meant to be filled with alternating layers of vanilla and chocolate buttercream, and covered in cream cheese frosting, but I settled for chocolate buttercream inside and out. Let that be a lesson - do not bake when stressed, especially when it's the night before your wedding.