RUMORED BUZZ ON KOI FISH VS GOLDFISH

I’ve hardly ever owned a koi betta before and I had been wanting to know if it’s ordinary for them to change hues fast? I’ve experienced my Galileo for nearly two weeks and in that point he’s gotten darker which is now modifying to become lighter.From what I am able to see it appears like a comet goldfish not a koi and that is Excellent new