If I put hex codes into my nickname, the entire hex code shows up in discord
is there a way to fix this?

paper 1.16.4 with discordSRV v1.23.0

I understand that if you put a '&' before the hex, it solves the problem but I'm also being requested to post this so normal hex also works incase of a future rewrite

You can use DiscordChatChannelGameFilters to filter those out, with a pattern such as #[a-fA-F\\d]{6}, so the full option would be:

DiscordChatChannelGameFilters: {"#[a-fA-F\\d]{6}": ""}