diff --git a/src/applications/differential/editor/DifferentialTransactionEditor.php b/src/applications/differential/editor/DifferentialTransactionEditor.php
--- a/src/applications/differential/editor/DifferentialTransactionEditor.php
+++ b/src/applications/differential/editor/DifferentialTransactionEditor.php
@@ -1827,8 +1827,30 @@
   }
 
   private function renderPatchHTMLForMail($patch) {
+    $patch_html_lines = array();
+    foreach (phutil_split_lines($patch) as $line) {
+      $len = strlen($line);
+      $color = null;
+      if ($len >= 1 && $line[0] == '+') {
+        $color = 'green';
+      } else if ($len >= 1 && $line[0] == '-') {
+        $color = 'red';
+      } else if ($len >= 2 && substr($line, 0, 2) == '@@') {
+        $color = 'purple';
+      }
+
+      $attrib = array();
+
+      if ($color) {
+        $attrib['style'] = "color:{$color};";
+      }
+
+      $patch_html_lines[] = phutil_tag('span', $attrib, $line);
+    }
+
     return phutil_tag('pre',
-      array('style' => 'font-family: monospace;'), $patch);
+      array('style' => 'font-family: monospace;'),
+      $patch_html_lines);
   }
 
   private function renderPatchForMail(DifferentialDiff $diff) {