diff -u b/core/modules/system/css/system.diff.css b/core/modules/system/css/system.diff.css
--- b/core/modules/system/css/system.diff.css
+++ b/core/modules/system/css/system.diff.css
@@ -1,26 +1,4 @@
 /**
- * Inline diff markup
- */
-span.diff-deleted {
-  color:#ccc;
-}
-span.diff-deleted img {
-  border: solid 2px #ccc;
-}
-span.diff-changed {
-  background:#ffb;
-}
-span.diff-changed img {
-  border:solid 2px #ffb;
-}
-span.diff-added {
-  background:#cfc;
-}
-span.diff-added img {
-  border: solid 2px #cfc;
-}
-
-/**
  * Traditional split diff theming
  */
 table.diff {
@@ -33,13 +11,6 @@
   background-color: inherit;
   border: none;
 }
-table.diff .diff-section-title,
-table.diff  .diff-section-title {
-  background-color: #f0f0ff;
-  font-size: 0.83em;
-  font-weight: bold;
-  padding: 0.1em 1em;
-}
 table.diff .diff-context {
   background-color: #fafafa;
 }
@@ -59,9 +30,6 @@
 table.diff .diff-marker {
   width: 1.4em;
 }
-table.diff .diff-content {
-  width: 50%;
-}
 table.diff th {
   padding-right: inherit;
 }