Currently, there are three special dies; Behir Blue, Illithid Purple, and Dragonflame Red. Scuffed Metal is the default dice, Behir Blue is suppose to have been unlocked for everyone on PC (Steam, GOG) in one of the recent patches, Dragonflame Red is from the "Deluxe Edition", and Illithid Purple is from the Collector's Edition. What this mod seeks to do is unlock these for everyone.
This is a somewhat experimental mod, but all I can say is "works on my machine". Unpatched versions may have issues, but it should work on any game that has unlocked Behir Blue. If anyone knows where any other special/locked-away content is located or have ideas on how it can be unlocked, leave a message and we'll see what we can do.
For installation, extract to the \AppData\Local\Larian Studios\Baldur's Gate 3\Mods folder of the installation directory, same as any other mods. That's it. No further installation should be necessary, and it should in fact be impossible to configure with BG3ModManager.
I claim no ownership or credit of any of this, and encourage anyone to pick it apart as they see fit or include it in whatever.
Have fun! ^^/