GitHub apply dark theme on private repo

github-apply-dark-theme-on-private-repos.user.js

// ==UserScript==
// @name         GitHub apply dark theme on private repo
// @namespace    https://github.com/benok/
// @description  Apply dark theme to your private repository pages on Github
// @match        https://github.com/*
// @run-at       document-idle
// @version      2022.11.30.0
// @homepage     https://gist.github.com/benok/301f7a9667a598202f10111af054ae77
// @downloadURL  https://gist.github.com/benok/301f7a9667a598202f10111af054ae77/raw/github-apply-dark-theme-on-private-repos.user.js
// @updateURL    https://gist.github.com/benok/301f7a9667a598202f10111af054ae77/raw/github-apply-dark-theme-on-private-repos.user.js
// @author       benok
// @grant        none
// @license      MIT
// ==/UserScript==

(function() {
    'use strict';

    if (document.querySelector('span.Label.Label--secondary').textContent == "Private") {
        console.log('private repo. set data-color-mode to dark');
        document.querySelector('html').setAttribute('data-color-mode', 'dark');
    } else {
        console.log('public repo. set data-color-mode to light');
        document.querySelector('html').setAttribute('data-color-mode', 'light');
    }
})();

Having trouble now.
Setting html's data-color-mode doesn't update the actual page theme. :-(
(Setting the default theme to dark, it works partially, but unstable. May be needed to change apply timing.)