I used standard tins, greased and lined with non stick paper, which I have found is the best way of cooking a cake. They just fall out of the tin when you're done, and you don't need to worry about scratching non stick surfaces.
I divided the mix into six different glasses, with about twice as much violet as red. I used Gel Colours which I bought from this wonderful shop in the city. Gel colouring adds brilliant, vibrant colour without adding liquid, and only a tiny amount was needed. The red colour was produced with the amount of gel that stuck to the end of a skewer.
I poured the violet into the tin, and let it settle to the edges. I then poured the blue into the center. It naturally forms a perfect circle, and pushes the violet colour aside. Following with the other colours, I ended up with this result...
Then, into the oven.