I have a chattag system that I found somewhere but I don't entirely remember where... I think it was on some forums or something and it's just a lua code that you put in lua/autorun or you can put in addons/[file name]/lua/autorun . I'll post the code I guess, it works good, but like I said, I don't remember where I found it so I can't give credit to the creator.
Edit: SEE BOTTOM
Obviously you would edit this to fit your groups and the code should be easy enough to follow. I have it in a file addons/chattags/lua/autorun/chattags.lua , but you can put it in a different addon folder name or directly into lua/autorun or wherever. Just make sure to keep the lua file as chattags.lua unless you want to change the line near the top AddCSLuaFile( "chattags.lua" ) to the right name of he file
There are many ways to set it up which should be pretty easy if you read through the code, by default it's something lik [Rank]name:message. With a little bit of changing you can easily change it to "Rank
| Name:Message" which is what I personally prefer, but obviously it's up to you. I'm not sure what gamemode you're using this in but for most gamemodes it should work fine, if it's ttt you might want to either remove the (TEAM) prefix so that innocents can't prove themself inno by typing in team chat, or just use another script that blocks innocents from being able to use teamchat.
Edit: I found the post that I got it from (I take no credit in making the code). It is
Herebut note: in the comments it appears that the actual original post might be
Here.