Weathering of roof tiles

Keith from England asked:

The roofer has used Sandtoft Double Roman Antique 2 and the house next door has had theirs done now for over 4 years. I would like to ask why our new down tile on the dormer matches but the tiles on the roof do not. My roofer is telling me that they will weather the same as next door. Can some one advise if this is correct. Many thanks.

Here is what one of our roofing experts, John Chan with The Durable Slate Company, had to say:

There is more than one reason for this.

On the right-hand side underneath the edge of the dormer, you can see a streak where more water comes down the roof. At that area, the excess water runoff causes that color difference.

As far as what the customer is asking, as the different batches of tile are produced, there are sometimes slight variations in color from one batch to another, but sometimes they're the same.

The tiles on the dormer are a perfect match, but the tiles on the roof are slightly off. This may or may not blend out over the years, but no one can say for sure, if it'll completely blend in or not, even though they're the same color from the same manufacturer.