At the top of the addon file, I'd give users the options of custom or default colour schemes.
Lua Code:
local CUSTOM_FACTION_BAR_COLORS = CUSTOM_FACTION_BAR_COLORS or FACTION_BAR_COLORS
local CUSTOM_CLASS_COLORS = CUSTOM_CLASS_COLORS or RAID_CLASS_COLORS
Class Colors, Curseforge:
https://www.curseforge.com/wow/addons/classcolors
Class Colors, Wowinterface:
https://www.wowinterface.com/downloa...assColors.html
Documentation:
https://github.com/phanx-wow/ClassColors/wiki
Obviously CUSTOM_FACTION_BAR_COLORS is unique to your addon but you could still provide some options.