Please allow us to easily change our own client sided highlight color. The current one sucks. Thank you.

This already exists. I made a tutorial on how to change it.

You can find it here: https://forum.toribash.com/showthread.php?t=648877

Pretty much already a thing as Kris pointed out.
If you want to have your messages shown in same color as everyone else's, use /opt playertext 0: https://store.steampowered.com/news/...59257880060488