DragonVale: How to Breed the Rainbow Dragon
In DragonVale for the iPhone and iPad, the Rainbow Dragon is one of the rarest of the epic rare dragons in the game.
To breed a Rainbow Dragon, you need to breed two dragons that have a total of at least four different elements combined. For example, a Glacier Dragon has Earth and Cold elements, while a Firefly Dragon has Fire and Lightning elements, so this combination has a chance to produce a Rainbow Dragon. There is no guarantee however, since it is still a rare random chance.
Breeding two Rainbow Dragons together however will always result in another Rainbow Dragon, so you can use this as a farming technique to sell them and make quite a bit of money.