The light brown colour is set on the <body> of your page, so to change it to the darker brown, you need to alter
change #DEB887 to #97694F
I'm not sure if Barnum wants to completely replace the light brown. I read it as wanting the area beneath the grey footer and the bottom of the viewport to be dark brown, matching the width of #container. If so...
Firstly, give #container overflow:hidden; so that it clears the floated ul. This will remove the gap at the bottom. Then, unless you'd prefer to let the page end with nothing below #footer, add padding-bottom to #container of however much dark brown area you wish to appear at the bottom. e.g.
background: none repeat scroll 0 0 #97694F;
overflow: hidden; /* added */
padding-bottom: 50px; /* added */
At present you have CSS for #container and other elements both in a separate stylesheet - styles.css - and in the embedded stylesheet within the head of your page. This could cause confusion and should be cleaned up but, for now, replace the CSS rule for #container in your embedded stylesheet - not styles.css - with the above.