As others suggest, a legend is the "index" that defines what is what within cartography. Seems a custom "category" that defines those elements that allows the author to choose colors/ symbology would be the approach.
If / when it becomes "shareable" via community or market place,the end user, can simply modify this category to make those global changes to suit their need or preference.
This would open the possibility for specialty token sets depicting anything from colors to styles to symbols from the community or market place that would subcategorize sets And "unlock if they choose" (like other structure already in place)
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