Rainbowcy is a challenge in which you create a nine generation legacy. It is very similar to the Not So Berry challenge but a whole new set of objectives.
All rules of the challenge apply to this aspiration. These rules can be found here: Challenge Rules.
It is best to also look at these rules to not only get the full scope of the challenge but also because all of the requirements weren't able to be converted into objectives for the aspiration.
There are 3 files in total for this aspiration.
The breakdown will be:
Part 1: White, Pale Pink or Purple, Peach, Orange
Part 2: Pale Yellow, Pale Green, Teal
Part 3: Pale Blue, Final Gen
It's giving the animal whisperer reward trait on parts one and two and thats because their is no actual reward upon completion on them so the game is just filling it in.