Squarespace injection

injected.html

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js"></script>
<script type="text/javascript" charset="utf-8">
  $(function() {
	    var path = window.location.pathname.toString();
	    var patterns = {
	        "about": /about$/i,
	        "contact": /contact$/i
	    };

	    for (colorBarClass in patterns) {
	        var pattern = patterns[colorBarClass];
	        if (pattern.test(path)) {
	            var colorBar = $("<div>").addClass("npl-color-bar").addClass(colorBarClass);
	            $("body").prepend(colorBar);
	            break;
	        }
	    }
	});
</script>

stylesheet.css

.npl-color-bar {
  width: 100%;
  height: 5px;
  position: absolute;
  top: 0;
}

.npl-color-bar.about {
  background-color: green;
}