On my neck, you will always see the black / blue beard line.
I remember a newbie on B & B who was "disappointed at the blue outline" after a shave. After some time and further posts, we discovered that he thought DE shaving would get rid of any trace of a beard at all, even under the skin. He had been shaving harder and harder and closer and closer to achieve this (god only knows what those shaves looked like, I could only picture him scraping several layers of skin off while muttering "Would you do me..? I'd do me...").