Get the avatar favorites keybind mod.
He means like an emote that makes your mouth move.
I don't think it is possib --- Nevermind, server-sided can do as well
It could be client sided. Just have a keybind in emotes that makes your face change between the 3 shown in the op. Unless you have one of those mods that restricts avatar changing so people don't do the color thing. That could break it.
That is an issue, some servers have the "Anti-Rainbow" thing.
But it is possible. I don't think many servers use that anymore.