JSFiddle - React, Tailwind, and code Playground

CSS

:root {
  --bg-color: linear-gradient();
}

body {
  background: var(--bg-color, white);
  background-repeat: no-repeat;
  min-height: 100vh;
  overflow: hidden;
}

JavaScript

(function randomBackground() {

  const linearGradients = [
    "linear-gradient(to right, #c6ffdd, #fbd786, #f7797d)",
    "linear-gradient(to right, #6a3093, #a044ff)",
    "linear-gradient(to right, #a8ff78, #78ffd6)",
    "linear-gradient(to right, #6d6027, #d3cbb8)",
    "linear-gradient(to right, #4da0b0, #d39d38)",
    "linear-gradient(to right, #74ebd5, #acb6e5)",
    "linear-gradient(to right, #12c2e9, #c471ed, #f64f59)",
    "linear-gradient(to right, #4b79a1, #283e51)",
    "linear-gradient(to right, #0099f7, #f11712)"
  ];

  const randomColor =
    linearGradients[Math.floor(Math.random() * linearGradients.length)];
  document.querySelector("body").style.setProperty("--bg-color", randomColor);
}());