Make entire stage white

src/components/stage-selector/stage-selector.css

@@ -10,7 +10,7 @@ $header-height: calc($stage-menu-height - 2px);
     position: relative; /* For the add backdrop button */
     flex-grow: 1;
     font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
-    background-color: #f9f9f9;
+    background-color: #fff;
     color: $text-primary;
     border-top-left-radius: $space;
     border-top-right-radius: $space;