First, you have named a file stylesheet_save.css and any file with the extention of css is parsed -
get rid of the .css extention for old copies name them stylesheet.old or anything but .css
Next you have broken your sheet named stylesheet.css
I suggest your delete it and rename stylesheet_save.css to stylesheet.css
Once that is done then find this code in the file and change the red highlighted value to the color you want
Code:
#navMainWrapper, #navSuppWrapper, #navCatTabsWrapper {
margin: 0em;
background-color: #9a9a9a;
font-weight: bold;
color: #ffffff;
height: 1%;
width: 100%;
}