<!DOCTYPE html>
<html>
<head>
  <title></title>
  <style type="text/css">
    div {
      width: 300px;
      height: 150px;
      background: conic-gradient(
        from 90deg at 100px 50px,
        red 0.2turn,
        orange 0.2turn 0.4turn,
        yellow 0.4turn 0.6turn,
        green 0.6turn 0.8turn,
        blue 0.8turn 1.0turn
      );
  </style>
</head>
<body>
  <div id="output"></div>
</body>
</html>