<title>My Example</title>
document.addEventListener("DOMContentLoaded", function(event) {
var e = document.getElementById("myForm");
e.addEventListener( "change", function() {
var myColor = this.color.value;
msg = "Just like the sky!";
else if (myColor == "Red") {
else if (myColor == "Green") {
document.getElementById("msg").innerHTML = msg;
<form id="myForm" name="myForm" action="{action page}">
<input type="radio" name="color" value="Blue"> Blue
<input type="radio" name="color" value="Red"> Red
<input type="radio" name="color" value="Green"> Green