Fix custom colors -bg-back, closes #269

.themes/classic/sass/custom/_colors.scss

@@ -12,7 +12,7 @@
 //$sidebar-link-color-hover: darken(#7ab662, 9);
 //$footer-bg: #ccc !default;
 //$footer-bg-front: image-url('noise.png');
-//$footer-bg-back: linear-gradient(lighten($footer-bg, 8), $footer-bg, darken($footer-
+//$footer-bg-back: linear-gradient(lighten($footer-bg, 8), $footer-bg, darken($footer-bg, 11));
 
 
 /* To use the light Solarized highlighting theme uncomment the following line */