CSS

RGB to HEX

https://css-tricks.com/converting-color-spaces-in-javascript/

function RGBToHex(rgb) {
  let sep = rgb.indexOf(",") > -1 ? "," : " ";
  rgb = rgb.substr(4).split(")")[0].split(sep);

  // Convert %s to 0–255
  for (let R in rgb) {
    let r = rgb[R];
    if (r.indexOf("%") > -1)
      rgb[R] = Math.round(r.substr(0,r.length - 1) / 100 * 255);
      /* Example:
      75% -> 191
      75/100 = 0.75, * 255 = 191.25 -> 191
      */
  }

Create Style element insert into document head

generateRulesAll(tableRef.current).then((css) => {
      const styleElement = document.createElement('style');
      styleElement.innerText = css;
      iframeRef?.current.contentWindow.document.head.appendChild(styleElement);
    });