change font color or background color

I don’t see any white background on that menu, I see instead a gradient from dark red to a slightly lighter red.
In any case, if you want to change that color you must first create a child theme, and then go to edit css and add the following instruction. The meaning should be clear even if you don’t know CSS. Background is the directive that changes the background. However, there are three different instructions, one for the Chrome browser (webkit), one for Firefox (moz) and one for IE. They all create the gradient that I see. You must change the colors of the gradient, if you use Firebug on Firefox or the developer tools on Chrome you should be able to test it.

#navmargins {
background: #340b0a;
background: -webkit-gradient(linear,left top,left bottom,from(#0f0201),to(#340b0a));
background: -moz-linear-gradient(top,#0f0201,#340b0a);
background: transparent\9;
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=’#0f0201′,endColorstr=’#340b0a’);
box-shadow: 0 1px 2px #000;
-moz-box-shadow: 0 1px 2px #000;
-webkit-box-shadow: 0 1px 2px #000;
}