<!DOCTYPE html>
<html>
<head>
<title>Putting BG color in a specific region</title>
<style>
#ABC {
background-color: blue;
height: 100%;
position: absolute;
top: 0;
left: 0;
width: 100%;
}
body{
background: grey;
margin: 0;
}
</style>
</head>
<body>
<section id="ABC">
</section>
</body>
</html>