html,body {
  width: 100vw;
  height: 100vh;
}

let getRandomColor = () => {
    let characters = '0123456789ABCDDEF'
    let color = '#'

    for (let i = 0; i < 6; i++) {
        color +=characters[getRandomNumber(0, 15)]
    }
    return color
}

let getRandomNumber = (min, max) => {
    let r = Math.floor(Math.random() * (max - min + 1)) + min
    return r
}

var color = getRandomColor()

document.body.style.backgroundColor = color;