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

{
  "type": "minecraft:crafting_shapeless",
  "group": "light_gray_dye",
  "ingredients": [
    {
      "item": "minecraft:black_dye"
    },
    {
      "item": "minecraft:white_dye"
    },
    {
      "item": "minecraft:white_dye"
    }
  ],
  "result": {
    "item": "minecraft:light_gray_dye",
    "count": 3
  }
}