Starting at the top:
5 rows of 3
This will give you 24 cupcakes
The top three and the bottom 2 rows will fit tightly together and be easier to ice,
leaving larger gaps in the middle section that will probably require more...
When I made this rainbow cake, I first tried to use crushed berries to colour the batter but the colours were not vibrant enough, so I added americolor gels.
I did not put any filling between the layers, just a few dabs of simple...