We've just had a new block paved driveway. Perfect workmanship from a reputable company. It's supposed to be a dark colour but has gone light due to the "natural salts coming through". Has anyone experienced this & did it just clear up naturally over time? We haven't paid yet, some people say don't pay & they should fix it, but from what it could just happen again. Should I tell them to fix it or let nature take its course?