There's no special recipe for this Rainbow Jello, except patience :( I could have made life easier for myself by simply making the jelly in its own flavour but itchy hands want to try the rainbow effect :p So all in all it took me 5-6 hours to complete the layers and another couple of hours to let the jelly properly.
Tortally is the most common brand of jelly found in our supermarkets; managed to find 5 flavours, Pineapple, Orange, Raspberry, Lime and Blackcurrant. I think Cold Storage or Jasons sell another brand Jell-O.
The package instructions say to mix 250ml of hot water to the jelly crystals, mix well then mix another 250ml of cold water. I wanted the jelly to be firmer so I used 200ml of hot water and 200ml of cold water. In between layers, I let the jelly chill in the fridge for about an hour before pouring another layer. Just need to be gentle when pouring the next layer to prevent creating air bubbles.
It's quite interesting to eat through the different layers to taste the different flavours of jello. I liked the raspberry taste best and hated the lime; I think the lime tasted quite yucky, like my dishwashing soap :(
Anyways, I will stick to single flavour next time. Too much work just for jello.