SOURCE

const domHtml = document.querySelector('html');
const domBtn = document.querySelector('button');
const domText = document.querySelector('p');

domBtn.addEventListener('click', toggleColor);
function toggleColor() {
    const code16 = randomColor();
    domHtml.style.backgroundColor = `rgb(${random(255)}, ${random(255)}, ${random(255)})`;
    domText.style.backgroundColor = code16;
    domText.textContent = `16进制 ${code16}`;
}
function random(num){
    return Math.floor(Math.random() * (num + 1));
}
function randomColor(){
	return '#'+ Math.floor(Math.random() * 0xffffff).toString(16).padEnd(6, '0');
}

<button type="button">toggle color</button>
<p>16进制</p>