But now, Blogger have improved this area. Blogger have added two new color schemes — "Transparent Light" and "Transparent Dark." These new color schemes take advantage of the ability of modern browsers to render transparency (a technique known to web designers as "alpha blending"). This allows the navbar background to blend together with your blog's background color and pattern. That's mean you can get this transparent navbar if you use modern browser, except Internet Explorer 6. This browser doesn't support transparent image.Why dont think to upgrade it? :D
To enable the Transparent Light or the Transparent Dark navbar, go to Layout | Page Elements, then click Edit next to the navbar widget
But, blogger navbar is hidden on my template. How to show that? Read this article How to Show Blogger Navbar.