To get the lines of colour in the piping, I painted lines with food colouring in the inside of the piping bag before filling it with the butter cream.
The last time I attempted a rainbow cake was around 2 years ago and I used liquid food colouring. I was disappointed with how the colours turned out, too pale. This time round I used Wilton concentrated food colouring, a small drop makes such a difference in the colour without changing the consistency of the mixture.
Fortunately I was able to see the inside of the cake and eat a slice too, of course. The colours of the layers were vibrant and stood out so well, and it tasted delicious too!
I had a few spoonfuls left of each colour cake mixture so popped them in a few white paper cake cases and mixed some of the cake crumbs in with the butter cream to top them.
Thanks for reading and I hoped you enjoyed it!