Added function to show BRG value to w3schools colors RGB

append_brg_value.user.js

// ==UserScript==
// @name         Append BRG Value
// @namespace    http://tyan0.dip.jp/~rei/
// @version      1.0
// @description  Added function to show BRG value to w3schools colors RGB
// @author       yanorei32
// @match        https://www.w3schools.com/colors/colors_rgb.asp
// @grant        none
// ==/UserScript==

// 以下のリンクからダウンロードすると、アップデートチェックしてくれるっぽいです
// https://gist.github.com/Yanorei32/08a5d10bea155200e6cdf3340f4fa4f3/raw/append_brg_value.user.js

;(function() {
    'use strict';
    let main = document.getElementById('main');

    let container = main.querySelector('.w3-container.w3-padding-large > .w3-row > .w3-col > .w3-large');
    let hex01 = document.getElementById('hex01');

    let brg = document.createElement('div');
    brg.classList.add('w3-margin-top');
    container.appendChild(brg);

    let update_brg = function(){
        let text = hex01.innerText.slice(1).match(/.{2}/g);
        let r = parseInt(text[0], 16).toString(10);
        let g = parseInt(text[1], 16).toString(10);
        let b = parseInt(text[2], 16).toString(10);

        brg.textContent = [b,r,g].join(',');
    };

    new MutationObserver(function(records){
        update_brg();
    }).observe(
        hex01,
        {
            childList: true,
            characterData: true
        }
    );

    brg.addEventListener('click', function(){
        let range = document.createRange();
        range.selectNodeContents(brg);
        let selection = window.getSelection();
        selection.removeAllRanges();
        selection.addRange(range);
    });

    update_brg();

})();