No need for plugins, client mods (optifine, although supported) or data packs.
This is fully functioning in vanilla java
This pack includes:

• Option 1: Resource pack for vanilla usage (usable with any plugins if you wish).
• Option 2: Oraxen files to import the armor in the plugin Oraxen.
• Instructions on how to use option 1 with MMOitems.
• Instructions on how to spawn the items in via commands (no plugins).

This pack works with most custom armor plugins like MMOItems, Oraxen or EcoArmor.

Adds textures for (you can call them what you want):

• Amethyst Armor
• Ruby Armor
• Onyx Armor
• Orax Armor