Untitled

<!DOCTYPE html>
    <html>
    <head>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
    <meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
    <title>Google Maps JavaScript API v3 Example: KmlLayer KML</title>
    <script src="http://code.jquery.com/jquery-1.4.4.js"></script>
    <script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script>
    <script type="text/javascript">
    $(document).ready(function(){
    $(".b_opacity").click(function(){
//this will find all the images in the map canvas container. Normally you would want to target specific images by the value of src
    $("#map_canvas").find("img").css("opacity","0.4")

    })
    })


    function initialize() {
      var chicago = new google.maps.LatLng(41.875696,-87.624207);
      var myOptions = {
        zoom: 11,
        center: chicago,
        mapTypeId: google.maps.MapTypeId.ROADMAP
      }

      var map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);

      var ctaLayer = new google.maps.KmlLayer('http://code.google.com/apis/kml/documentation/KML_Samples.kml');
      ctaLayer.setMap(map);
    }
    </script>
    </head>
    <body onload="initialize()">

      <div id="map_canvas" style="width: 600px;height: 600px;"></div>
      <input type="button" value="dim the lights" class="b_opacity">
    </body>
    </html>

#map > div > div > div > div > div:nth-child(2) img[draggable="false"] {
  opacity: 0.4;
}