I'm curious -- the miracle potion in the cash shop, what are its color options?
Iirc, one lets you change to any species (nonzappable/limited/cs excluded) without losing the color and one lets you change to any color without changing the species.
SubetaLodge sums it up better, lol.

Miracle Potion Allows you to pick ANY color that is available for the pet species you choose to use it on. You can see a full list of available colors here
Miracle Potion II changes your pets species and retains the pets color (if available).
It's always best to compare the shop prices of the Miracle Potion, CSC (to buy it yourself from the cash shop), and the price of the actual potion you are trying to change to in order to get the best deal.
Miracle Potion isn't worth it compared to any color, now :(
As for Miracle Potion II, some experiments come in Chibi, and all experiments come in Scribble