<!DOCTYPE html>
<html>
<head>
<style>
input[type=text]:enabled {
background: #ffff00;
}
input[type=text]:disabled {
background: #dddddd;
}
</style>
</head>
<body>
<form action="">
First name: <input type="text" value="Mickey"><br>
Last name: <input type="text" value="Mouse"><br>
Country: <input type="text" disabled="disabled" value="Disneyland">
</form>
</body>
</html>