find a single tag in a mongodb query

I want to fetch tags that only contains 'black', But when I run the query I get tags that contains black and some other color. How can I get tags that contains only black?.

Here is what I tried

const express = require('express');
const Inventory = require('../models/inventory');
const router = express.Router();

router.get('/inventory2', async (req, res) => {

  const inventory = await Inventory.find({
    tags: 'black',
  });
 
  res.send(inventory);
});

Here is what I was expecting

[
 {
    size: { h: 22, w: 30.5, uom: 'cm' },
    _id: new ObjectId("643cda1ccfda6cc57d5948ba"),
    item: 'table',
    qty: 851,
    tags: [ 'black' ],
    status: 'D'
 }
]

Here is what I got:

[
  {
    size: { h: 14, w: 21, uom: 'cm' },
    _id: new ObjectId("643cd5ef705862daba5fa9e7"),
    item: 'journal',
    qty: 25,
    tags: [ 'black', 'red' ],
    status: 'A',
    __v: 0
  },
  {
    size: { h: 22, w: 30.5, uom: 'cm' },
    _id: new ObjectId("643cda1ccfda6cc57d5948ba"),
    item: 'table',
    qty: 851,
    tags: [ 'black' ],
    status: 'D'
  }
]

You can add query for size so it will fetch the tags that have only specified size that will be 1

const inventory = await Inventory.find({
    tags: 'black',
    tags: {$size : 1}
  });

or you can exclude other colors also

const inventory = await Inventory.find({
    tags: 'black',
    tags: {$nin: ['red', 'green']}
  });