minecraft-assets/assets/minecraft/items/firework_star.json

{
  "model": {
    "type": "minecraft:model",
    "model": "minecraft:item/firework_star",
    "tints": [
      {
        "type": "minecraft:constant",
        "value": -1
      },
      {
        "type": "minecraft:firework",
        "default": -7697782
      }
    ]
  }
}