The way i explain the "greyed out look", is that as we are dealing with a synthetic pile,
imagine a nice shiny new pop bottle on the shelf, now kick it around the floor a bit, until
it is all scuffed up. it will look completly different, all the scratches reflect the light
differently appearing to be a different colour. the same thing has happened to the pile
through wear and tear.
I then tell them a BW is virtually impossible to wear out in normal use, but aesthetically
the looks will degrade over time.