<script type="text/javascript">
function changeColor (thisColor) {
 document.getElementById('myMsg').style.borderColor = thisColor;
}
</script>
<div id="myMsg" contextmenu="myMenu" style="width:50%;padding:0.5em;border:10px solid black;">
<p>Right click on the me to invoke the context menu (look for <samp>Change Border Color...</samp>).</p> 
<p><strong>Note</strong>: Only supported in Firefox at time of writing.</p>
</div>
<menu type="context" id="myMenu">
 <menu type="popup" label="Change Border Color...">
  <menuitem label="Black (default)" onclick="changeColor('black');"></menuitem>
  <menuitem label="Orange" onclick="changeColor('orange');"></menuitem>
  <menuitem label="Red" onclick="changeColor('red');"></menuitem>
  <menuitem label="Green" onclick="changeColor('green');"></menuitem>
  <menuitem label="Blue" onclick="changeColor('blue');"></menuitem>
 </menu>
</menu>