Changing CSS in Gmail's iframe content with jQuery

Trying to change the nav bar in Gmail to a different color. What I have below is not picking up the canvas_frame even though I can see it when I view the source?

What am I doing wrong?

$(document).ready(function() {
  if ($("#ca开发者_C百科nvas_frame").length) {
  $("#canvas_frame").load(function() {
     $("#canvas_frame").contents().find(".qp").css("background-color","#FF0000");
    });
  }
});

How are you running your Javascript code? I can change the colour by following these steps -

• Open Firefox (with Firebug installed)
• Install jquerify bookmarklet (http://www.learningjquery.com/2009/04/better-stronger-safer-jquerify-bookmarklet)
• Go to GMail and run the bookmarklet

If I then run the following code in the Firebug console window the colour changes -

jQuery("#canvas_frame").contents().find(".qp").css("background-color","#00ff00");