JSFiddle - React, Tailwind, and code Playground

HTML

<div id="root">
</div>

JavaScript

function hexCode(num) {
  let converted = num.toString(16).toUpperCase();
  if (converted == 100) return "FF";
  else if (converted < 10) return "0" + converted;
  return converted;
}

function hexColor(num1, num2) {
  let colour = "#";
  colour += hexCode(num1) + hexCode(num2) + "00";
  return colour;
}

function createCell(colour) {
  let cell = document.createElement("td");
  cell.style.width = "10px";
  cell.style.height = "10px";
  cell.style.backgroundColor = colour;
  cell.title = colour;
  return cell;
}

let root = document.getElementById("root");

for (i = 0; i <= 256; i += 16) {
  let row = document.createElement("tr");
  for (j = 0; j <= 256; j += 16) {
    let colour = hexColor(j, i);
    let cell = createCell(colour);
    row.appendChild(cell);
  }
  root.appendChild(row);
}