Change diff colors

Now uses higher contrast colors for the diff.

Bug: Issue 8927
Change-Id: Iafa5b2fa94b295471fc6b02e4eaaecd00271ffdb
diff --git a/polygerrit-ui/app/styles/themes/app-theme.html b/polygerrit-ui/app/styles/themes/app-theme.html
index 4500e10..6d24762 100644
--- a/polygerrit-ui/app/styles/themes/app-theme.html
+++ b/polygerrit-ui/app/styles/themes/app-theme.html
@@ -78,14 +78,14 @@
 
   /* Diff colors */
   --diff-selection-background-color: #c7dbf9;
-  --light-remove-highlight-color: #fee;
-  --light-add-highlight-color: #efe;
-  --light-remove-add-highlight-color: #fff6ea;
-  --light-rebased-add-highlight-color: #edfffa;
-  --dark-remove-highlight-color: rgba(255, 0, 0, 0.15);
-  --dark-add-highlight-color: rgba(0, 255, 0, 0.15);
-  --dark-rebased-remove-highlight-color: rgba(255, 139, 6, 0.15);
-  --dark-rebased-add-highlight-color: rgba(11, 255, 155, 0.15);
+  --light-remove-highlight-color: #FFEBEE;
+  --light-add-highlight-color: #D8FED8;
+  --light-remove-add-highlight-color: #FFF8DC;
+  --light-rebased-add-highlight-color: #EEEEFF;
+  --dark-remove-highlight-color: #FFCDD2;
+  --dark-add-highlight-color: #AAF2AA;
+  --dark-rebased-remove-highlight-color: #F7E8B7;
+  --dark-rebased-add-highlight-color: #D7D7F9;
   --diff-context-control-color: #fff7d4;
   --diff-context-control-border-color: #f6e6a5;
   --diff-tab-indicator-color: var(--deemphasized-text-color);