Issue #3198988: Provide legacy support for all colour options

sass/_mobile-menu.scss

-.govuk-header {
-  #block-mainnavigation {
-    display: none;
-    @include govuk-media-query($from: desktop) {
-      display: block;
-    }
-  }
-  .hamburger {
-    float: right;
-    color: govuk-colour("white");
-    font-size: 26px;
-    cursor: pointer;
-    padding-left: 15px;
-    @include govuk-media-query($from: desktop) {
-      display: none;
-    }
-  }
-  #mobile-menu {
-    position: relative;
-    width: 100%;
-    #mobile-menu-content {
-      display: none;
-      position: absolute;
-      top: 0;
-      left: 0;
-      z-index: 1;
-      background-color: govuk-colour("black");
-      width: 100%;
-      .govuk-header__navigation {
-        display: block;
-        padding: 0 15px;
-        li {
-          padding: 0;
-          font-size: 20px;
-          a {
-            padding: 20px 0;
-            width: 100%;
-            display: block;
-          }
-        }
-      }
-    }
-  }
-}
\ No newline at end of file
+.govuk-header {
+  #block-mainnavigation {
+    display: none;
+    @include govuk-media-query($from: desktop) {
+      display: block;
+    }
+  }
+  .hamburger {
+    float: right;
+    color: govuk-colour("white");
+    font-size: 26px;
+    cursor: pointer;
+    padding-left: 15px;
+    @include govuk-media-query($from: desktop) {
+      display: none;
+    }
+  }
+  #mobile-menu {
+    position: relative;
+    width: 100%;
+    #mobile-menu-content {
+      display: none;
+      position: absolute;
+      top: 0;
+      left: 0;
+      z-index: 1;
+      background-color: govuk-colour("black");
+      width: 100%;
+      .govuk-header__navigation {
+        display: block;
+        padding: 0 15px;
+        li {
+          padding: 0;
+          font-size: 20px;
+          a {
+            padding: 20px 0;
+            width: 100%;
+            display: block;
+          }
+        }
+      }
+    }
+  }
+}