Some pets don't have two types of purple, so indigo and violet will just be purple. It goes, red, orange, yellow, green, blue, purple. PPS are totally fine as long as they are the same species.
There are no rules, but please be courteous to other players. Try not start with a pet species that either doesn't have the full rainbow color, or are really hard to acquire. Malk dragons and Tess horses are two examples.
Here is an example on what it might look like.
Etc.
I really hope this game is allowed since it is inspired from a different game.
Both me AND my sister Lovebean can redirect the pets if the species accidently changes.