Skin Discoloration Around Healed Scar

I had surgery six years ago and the scar is fully healed, but in one spot there is a splotch of red discoloration which brings attention to the scar when it might otherwise go unnoticed.  The scar itself healed nicely and has gone back to a natural skin color.  Recently I saw a plastic surgeon to ask about scar revision, and he said that the color was not related to the scar at all but had some other cause.  He pointed out that the scar itself is nice and flat, meaning the scar was healthy, and suggested that the red may be from an ingrown hair or something.

The area is not itchy or tender at all.  It has been like this ever since the surgery, so I am convinced that it had something to do with the trauma to the skin from the surgery.  But what could possibly be the source if not the scar, itself?  I am very frustrated because I don't know how to go about treating this now.  And as I said, were it not for the redness I think the scar would not be noticed at all.