Mike Bostock tip on moving elements in front of siblings. https://groups.google.com/forum/#!msg/d3-js/eUEJWSSWDRY/EMmufH2KP8MJ

gistfile1.txt

  d3.selection.prototype.moveToFront = function() {
    return this.each(function() {
      this.parentNode.appendChild(this);
    });
  };

Then you can say:

  d3.select("p").moveToFront().style("color", "red");