In OSRS corp drops the core, and you are able to switch between the critter and the core. Making the core drop the core pet and the corp drop the critter is just stupid. Same with zulrah pet, KQ and a couple more.
I know how the pet works on OSRS. I think you should be able to choose between colors once you get any of the pets that there are multiple colors of. Also Just my opinion on how it should drop, we're all allowed to have one