There's not much to document.
There is a config.yml that allows you to toggle if you want to allow players to use hex colors on signs/chat.

Commands:
/hexsigns <text/sign> <enable/disable>
/hexsigns-reload

Permissions:
fjc.hexsigns.edit - allows players to set colors. Set to true by default.
fjc.hexsigns.admin - Admin privileges. Set to OP access only by default.