darker background for increased contrast

lms/static/sass/base/_variables.scss

@@ -23,6 +23,7 @@ $yellow: rgb(255, 252, 221);
 $error-red: rgb(253, 87, 87);
 $border-color: #C8C8C8;
 $sidebar-color: #f6f6f6;
+$outer-border-color: #aaa;
 
 // old variables
 

lms/static/sass/course/base/_base.scss

 body {
   min-width: 980px;
   min-height: 100%;
-  background: url(../images/bg-texture.png) #f7f7f7;
+  background: url(../images/bg-texture.png) #ddd;
 }
 
 body, h1, h2, h3, h4, h5, h6, p, p a:link, p a:visited, a, label {
@@ -33,7 +33,7 @@ a {
     table-layout: fixed;
     width: 100%;
     border-radius: 3px;
-    border: 1px solid #ccc;
+    border: 1px solid $outer-border-color;
     background: #fff;
     @include box-shadow(0 1px 2px rgba(0, 0, 0, 0.05));
   }

lms/static/sass/course/layout/_courseware_header.scss

@@ -35,7 +35,7 @@ nav.course-material {
 
         &:hover {
           color: #333;
-          background: rgba(0, 0, 0, .08);
+          background: rgba(255, 255, 255, .4);
         }
 
         &.active {
@@ -56,7 +56,7 @@ nav.course-material {
 }
 
 header.global.slim {
-  border-bottom: 1px solid #bbb;
+  border-bottom: 1px solid $outer-border-color;
   @include box-shadow(0 1px 2px rgba(0, 0, 0, .1));
   height: 50px;
   @include linear-gradient(top, #fff, #eee);