<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>arrow icon</title>
</head>
<body>
  <div class="arrow-explain1"></div>
</body>
</html>
div + div {
  margin-top: 30px;
}
.arrow-explain1 {
  width: 30px;
  height: 30px;
  border-top: 30px solid #cc0000;
  border-right:  30px solid #cccc00;
  border-bottom:  30px solid #00cc00;
  border-left:  30px solid #0000cc;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.