static @Nullable Color getFileBackgroundColor(@Nullable Project project, @Nullable VirtualFile file) {
    if (project == null || project.isDisposed()) return null;
    if (file == null || !file.isValid()) return null;
    return getInstance(project).getFileBackgroundColor(file);
  }
static @Nullable Color getFileBackgroundColor(@Nullable Project project, @Nullable VirtualFile file)