It seems that making local chat another color is not hardcoded.
I've been playing on another server with local chat aswell, and this chat popped up as Orange colored chat.
Indeed, you guys do reply fast hehe.
I can gife the admin that goes over this local chat some info about the server with had local chat in orange (so you can talk with those admins how to change it) I'm sure those admins will be able to help a hand. It would be very wise to make it Orange (or a other color if possible) so people know it's local, so we don't have to type (local) behind every message because that just costs time.. and time is money!
Anyways I'll be hoping to hear a voice from the admins about this, as we all seem to want it back. But without confusion.