How do I have different appearance for the same fish?

[oni]

Hi,
I am currently working on a fish mod, I was wondering if I could have multiple images for the same fish as their variety, without adding them as a new fish. Kinda like how fairy rose can have different flowers colors and they are randomize. I assume you can change it in this code but I don't know how to

"Changes":[
{
"LogName":"Betta fish load",
"Action": "Load",
"Target":"Mods/loopy.bettafish/AquariumBetta, Mods/loopy.bettafish/bettaFish",
"FromFile":"assests/{{TargetWithoutPath}}.png"
},

Appreciate for any help!