Index: wp-content/themes/twentytwelve/style.css
===================================================================
--- wp-content/themes/twentytwelve/style.css	(revision 21334)
+++ wp-content/themes/twentytwelve/style.css	(working copy)
@@ -944,12 +944,13 @@
 	margin: 1.714285714rem 0;
 	padding: 24px;
 	padding: 1.714285714rem;
-	line-height: 1.714285714;
 	font-family: Consolas, Monaco, Lucida Console, monospace;
 	font-size: 12px;
 	font-size: 0.857142857rem;
-	line-height: 2;
+	line-height: 1.714285714;
+	color: #666;
 	overflow: auto;
+	border: 1px solid #ededed;
 }
 .entry-content pre code,
 .comment-content pre code {