minecraft-assets/data/minecraft/trim_material/gold.json

{
  "asset_name": "gold",
  "description": {
    "color": "#DEB12D",
    "translate": "trim_material.minecraft.gold"
  },
  "ingredient": "minecraft:gold_ingot",
  "override_armor_assets": {
    "minecraft:gold": "gold_darker"
  }
}