Why do I have a weird red pigment on my lip?

I don't know if I have had this before, but I haven't noticed until now. My top lip, right smack dab in the middle is a red color, the rest of my lips are pink. I don't think it's that noticeable, but why is it like that? It doesn't hurt or anything and has been there for a couple months. I was tested and came back neg for everything except HSV-1 (oral ). I have never had an outbreak or anything, but could this be from contracting oral ?