A rewrite of the answer by Sarfraz would be something like this, I think:
<script>
document.getElementById('change').onclick = changeColor;
function changeColor() {
document.body.style.color = "purple";
return false;
}
</script>
You'd either have to put this script at the bottom of your page, right before the closing body tag, or put the handler assignment in a function called onload - or if you're using jQuery there's the very elegant $(document).ready(function() { ... } );
Note that when you assign event handlers this way, it takes the functionality out of your HTML. Also note you set it equal to the function name -- no (). If you did onclick = myFunc();
the function would actually execute when the handler is being set.
And I'm curious -- you knew enough to script changing the background color, but not the text color? strange:)