How can I invoke a custom item modifier from a loot table entry?

Hello, I have a loot table which sets armor for pillagers (from the Illagers Wear Armor mod) and I'm trying to create an item function for setting the color of leather armor. The reason I want to create a separate item function file is because this would be used a lot for the different armor sets that I'd be using, so it'd cut down on repetition by a lot. By the way, I can absolutely make this work without the use of a separate item function file, but that'd be tedious.
Anyway, here's how I've got it set up right now:
This is the entry in the loot table pool for boots:
            "type": "minecraft:item",
            "name": "minecraft:leather_boots",
            "weight": 2,
            "functions": [
              {
                "function": "musketcraft:color_leather_armor"
              }
            ]
   }```
The item function is located here: `data/musketcraft/item_modifiers/color_leather_armor.json` and it looks like this:

[
    {
        "function": "minecraft:set_nbt",
        "tag": "{display: {color: 12692378}}"
    }
]
I'm using a list because I'm going to expand it to include the possibility of other colors. But for now, it will only have one color. Thank you!