message: style(Navigation): use mid level gray for background
diff: // Top level styles should be nested here
  &#{&} {
  @include typography;
  - background: color(pure, dark);
  + background-color: color(utility, dark);
  color: color(pure);
  }
  }
  ::ng-deep .mat-menu-content {
  - background-color: color(pure, dark);
  + background-color: color(utility, dark);
  // override material styles
  padding: 0;
  