That works if you haven't set a new topcolor. (Actually, even for people who have set a custom topcolor, many HN pages still display the default topcolor, so the point in the parent post is correct.)
Also, being able to set the topcolor takes some non-trivial amount of karma, so you would have to have been using the site for a while in its default look anyhow.
That works if you haven't set a new topcolor. (Actually, even for people who have set a custom topcolor, many HN pages still display the default topcolor, so the point in the parent post is correct.)