Heyo! For people who don't know me, I'm Apple, I'm a certified Horse Girl™ (gender neutral)
I've been a fan of horses my whole life, having over 10 years of riding experience, and really got into horse genetics when I entered the Horse Art RPG community as a pre-teen.

So when the Tobiano, Overo, and Tovero came out this year as the piebald bases, I celebrated! For those who don't know, those are 3 of the types of paint a horse can be! But there's some fun little tidbits that come with breeding those coat patterns: they often interact with each other in weird ways!

The first thing I'll clear up is that the Lioden's Tovero marking is closer to a Tobiano, Tovero's would be significantly more white, but I understand hiding the majority of the markings won't be good in this game, so I'll let it slide!
I'll be instead using a more horse-accurate tovero for ease of understanding the different outcomes
->

Welcome back to your High School Bio Class, we'll be doing some Punnett squares >:)

So OBVIOUSLY I won't do pattern-less to pattern-less.

First up, Tobianos


Overo Next!


Tovero!


So, why am I showing you Punnett squares with horses you may ask? "Apple, this isn't lions" you may be screeching at your screen.

Well, I'm suggesting making them slightly different than a typical Pie. Making them a more realistic version and potentially bringing in a new lethal cub into the game! While I know the odds of it being this high, I'm suggesting that whenever it falls into a specific slot, whatever pie is there, it'll have a chance to roll.

So like, instead of Tobiano and Tobiano causing a 75% chance of producing a Tobiano, it'd have a 75% chance of rolling it the regular pie's natural 5% chance of being a Tobiano.

"But Apple," you may say, "Doesn't that reduce the likelihood of mutations?!" Yes, BUT Overo and Tovero have a very slight chance of producing a Lethal White, which would be a new lethal, AND you could have a chance at a different mutie, much how like Primals can give you different variations!

Not only that, but you'd have the chance to have the first lethal that isn't 100% chance based, therefore increasing the value of Overo and Toveros.

"So, aren't the Tobianos getting the shorter straw here?" Kinda, unless, like my comment above, make the current Tovero into a Homozygous Tobiano, and not making the Tovero a MoD, therefore breeding the Tobiano would be vital into getting a Tovero, which would increase the odds of a Lethal white OR a Mutie vs the Overos.

TLDR: Make them have all slightly less likelihood of passing, but make it possible to combine them, while having the rare chance of producing a new lethal!

I may know some things about horse genetics, but I don't know anything about coding, so if somebody wants to tell me it's impossible, I'll take my Punnett squares and leave.

Guide for the colors below!