minecraft-assets/data/minecraft/recipes/brown_carpet_from_light_gray_carpet.json

{
  "type": "minecraft:crafting_shapeless",
  "category": "building",
  "group": "brown_carpet",
  "ingredients": [
    {
      "item": "minecraft:brown_dye"
    },
    {
      "item": "minecraft:light_gray_carpet"
    }
  ],
  "result": {
    "item": "minecraft:brown_carpet"
  }
}