Fixed preview background in SW theme

boards/static/css/sw/base_page.css

@@ -425,4 +425,9 b' audio {'
 
 #quote-button:hover {
     background-color: #b9c4e2;
-}
  No newline at end of file
+}
+
+#preview-text {
+    background: #FFF;
+    color: #000;
+}