To set the color, we add a color value at the end.

Set the border color to the value red.

<html>
<head>
<style>
.caution {
border: solid 10px red;
}
</style>
<link rel="stylesheet" href="style.css">
</head>
<body>
<h1 class="caution"> BREAKING NEWS!!! </h1>
</body>
</html>]]>

Make sure to type red.