<!DOCTYPE html>
<!--
 | Setting the border color.
 |   https://www.w3.org/TR/css3-background/#border-color
 -->
<html>
<head>
  <style>
    div {
      border: solid;
      border-color: #ff6363;
      height: 100px;
      width: 100px;
    }
  </style>
</head>
<body>
  <div></div>
</body>
</html>