Well Sbenny, its not really the facebook app, its a messenger for facebook or its a chat box. If you have a facebook account, you can log in the app to know. If you know where they can change nicknames, and chat colours, go to your chatmate chatbox and click the "i" with circle on upper right. You will see it. Now, i want my chatmate to have no permission on changing it.
Hmmm I think the only way to make this "hack" to work would be to make em install the mod if I ever succeed in making it.
Also, there are very good chances it's managed by Facebook (server side) and not by the app itself.