So, I altered the "init\std\base\char\brain\code\ref\setting_ref.dat" file to add another hair color, but it isn't showing up as an option in game. Do I have to add/edit code in another file somewhere to have the changes go through, or did I forget something in the setting_ref.dat file?

Add new options to stat_*.dat files in \init\stories\dungeon\settings\ folder.

Ah... now it's showing up.

Next question, what is the range of values for the RGBA if it is clearly far more than 0-255?

Depending on color depth it's either going to be 1023, 4095, 16383, 65535 or 16777215.

I thought that modern computers only did the "millions of colors" with the 0-255 RGB values.