In my lore, Unicorn Folk aren’t all that common but they do still have a social structure. And part of that had to do with the formation of their horns and sin. So when a unicorn sins, their horn changes and greys. BUT that’s only if they think what they did is a sin. So Belladonna, her horn curls at the top because she transitioned. However it didn’t grey because, to her, it’s not disgusting or sinful. She simply changed her path in life.

I have another character, Isadora, who is also a unicorn, abandon her herd over greed. She realizes just how bad it was because her herd isn’t alive anymore. Her horn conclaves on itself and has turned darker. She did something she regrets and has viewed as a sin so her horn changes.

Someone had brought up that if a unicorn murders someone but they perceive it as morally right, would their horn change? No. It’s all based on your own perception of what you do, and what you think is right.

It’s the idea that how you are raised shapes your view on how you view yourself and the morals you have.