restore color

src/client/styles/scss/_page-history.scss

@@ -28,12 +28,21 @@
 
 .comparison-header {
   height: 34px;
+  background-color: #ffffff;
+  border: 1px solid $gray-300;
   .comparison-source-wrapper {
     height: 26px;
     margin-right: 1px;
+    border-right: 1px solid $gray-300;
+    .comparison-source {
+      color: $gray-500;
+    }
   }
   .comparison-target-wrapper {
     height: 26px;
+    .comparison-target {
+      color: $gray-500;
+    }
   }
 }
 

src/client/styles/scss/theme/_apply-colors.scss

@@ -581,20 +581,3 @@ mark.rbt-highlight-text {
 .grw-btn-page-management:focus {
   background-color: rgba($color-link, 0.15);
 }
-
-// Revision comparison header
-.comparison-header {
-  background-color: #ffffff;
-  border: 1px solid $bordercolor-nav-tabs;
-  .comparison-source-wrapper {
-    border-right: 1px solid $bordercolor-nav-tabs;
-    .comparison-source {
-      color: $gray-500;
-    }
-  }
-  .comparison-target-wrapper {
-    .comparison-target {
-      color: $gray-500;
-    }
-  }
-}