diff --git a/res/themes/dark/css/_dark.scss b/res/themes/dark/css/_dark.scss
index d28efbb11f..a3515a9d99 100644
--- a/res/themes/dark/css/_dark.scss
+++ b/res/themes/dark/css/_dark.scss
@@ -246,3 +246,13 @@ $user-tile-hover-bg-color: $header-panel-bg-color;
         }
     }
 }
+
+// diff highlight colors
+// intentionally swapped to avoid inversion
+.hljs-addition {
+    background: #fdd;
+}
+
+.hljs-deletion {
+    background: #dfd;
+}
diff --git a/res/themes/light/css/_light.scss b/res/themes/light/css/_light.scss
index ac9cb261d3..288fb3cadc 100644
--- a/res/themes/light/css/_light.scss
+++ b/res/themes/light/css/_light.scss
@@ -341,3 +341,12 @@ $user-tile-hover-bg-color: $header-panel-bg-color;
     color: $accent-color;
     text-decoration: none;
 }
+
+// diff highlight colors
+.hljs-addition {
+    background: #dfd;
+}
+
+.hljs-deletion {
+    background: #fdd;
+}