the key thing to understand is that the plugin only loads the style sheet may it be from the default set of toolbar colors or from the plugin Admin Color Schemes which means the stylesheet were intended to be used in the dashboard and not in the front-end of your website.
here is what i did to fix it by using a simple css declaration,
since the css on the dashboard style sheets declares a background color(#f3f3f3) on the html element this is likely the cause of that weird space created under the wptoolbar (it depends by the way on what browser you are using because browsers still to this day handles the cascade of stylesheets very differently from one another)
html {
background-color: transparent;
}
hope it helps
