If you get a elixir e.g: Demi Elixir will it only change its species but not its colour?

If you use a Demi Elixir on your pet, it will change to a COMMON Demi. To change species while keeping the color, you'd have to use a Miracle Potion II.

awww but there sooo expensive! I might as well buy a potion of purity and change it again