A section of render on the side of our house was damaged when we were having the coping stones of the flat roof replaced on our extension. It's been repair patched but where it has been painted it now looks glaringly white compared to the rest of the render. Its right on the most visible bit of the house and is about a foot long in a big wedge that looks dreadful. It also makes the rest of the (actually pretty clean) render look filthy and patchy and a bit damp (which it's not, its just older and has natural weathering). Our house is about to go on the market and i'm worried it will make people thing the house is damp or that there is something wrong. But the house is huge and three storeys high so painting the whole side again is out of the question as it'd cost a fortune. I really want to try and weather the new patch to make it less noticeable but I can't work out what to do. The new bit has been painted in Dulux Weathershield which seems pretty slick and my experiments painting dirty water on it have done nothing at all - it just runs off. Any ideas what I can do to make it look a bit more dirty?