Regarding the commentary, that's what happens to real-life grey horses. They start out black/dark colored, and the color fades over time, often in different portions of the body, until it eventually becomes all grey.

BrokenEagle98 said in comment #2592389:

Regarding the commentary, that's what happens to real-life grey horses. They start out black/dark colored, and the color fades over time, often in different portions of the body, until it eventually becomes all grey.

I do wonder why their genes do that, it has to be something that only happens to domesticated horse because I don't see any use of that in the wild. If anything, it would make you a bigger target for predators

BrokenEagle98 said in comment #2592389:

Regarding the commentary, that's what happens to real-life grey horses. They start out black/dark colored, and the color fades over time, often in different portions of the body, until it eventually becomes all grey.

Looking at all the gray coats (ie. Oguri, Golshi, etc), that's definitely the case. Back when they were racing they had much darker coat but later in life they all become gray.

And this was also brought up in Uma!Chrono's secret as well in fact; which makes it clear that her hair color is getting lighter and lighter.