It is just a matter of time before this comes to a Cash Shop near you in GMS.
A new Pink Bean pet has been released, what makes this one unique (other than the attack bonuses for having it out, just like the Demon pets) is that its colour can be changed! After buying a Pet Color Change coupon in the Cash Shop, you can use the colour scrollers to change how your pet looks~
Courtesy Max's Blog.
I can see this being adapted for all pets in GMS since NexonAM would want to maximize how much $$$ it can squeeze from its players.