gunpowder-cocktail-client/minecraft/config/creativecore-client.json

{
  "use-stencil": true,
  "use-optifine-compat": true,
  "palette": [
    {
      "name": "basic",
      "colors": [
        -1,
        -16777216,
        -65536,
        -16711936,
        -16776961
      ]
    }
  ]
}