You are getting that black from image in css and to make it white you will need make few changes
look for this code
#holder {
background:transparent url(images/bcg.gif) repeat-y scroll center center;
float:left;
width:968px;
change this line
background:transparent url(images/bcg.gif) repeat-y scroll
to
background:#FFFFFF;
Do same for sidebar so you will have
#sidebar {
background:#FFFFFF;
display:inline;
float:left;
margin:0 5px 0 0;
padding:10px;
width:193px;
change font color in sidebar
#sidebar ul li a {
color:#E4F2FF;
font-size:14px;
text-decoration:none;
Change #E4F2FF to color you want
You will have change the hover color as well as they are white
#sidebar ul li ul li a:hover, #sidebar ul li a:hover {
color:#FFFFFF
