This resource pack changes all the emeralds that appear in the game to rubies like they originally were. These changes include the ores, beacon gui, totem of undying eyes, hero of the village symbol, armor trims, etc.
As an added bonus, if you were to type /give @s minecraft:ruby or /give @s minecraft:emerald it would still give you a ruby. This is true for all of the ruby items.
Website linked here.
Bug report and git repo on the site.
