Header Transparency

I’m trying to make just the area around a custom header transparent. Any idea on how to do this? I’ve tried every thing from putting it in custom style css, direct editing the style.css file and editing the header.php file (don’t worry I kept a copy of the originals and put them up after every failed attempt). I’ve put the code background-color: transparent in the #header but the #wrapper either ignores it or makes the whole page transparent.
hemlockcampground.com
Please any idea would help!