I have read that an asphalt shingle roof should not be pressure washed,
but I have also read that it is ok at low pressure.

Using low pressure, a guy pressure washed my asphalt shingle roof. Now
there are some irregular areas that are lighter than the rest. The
chairman of the board (my wife) does not like this. I think the guy
said the lighter areas are the color the shingles are supposed to be
(the color they originally were) and the darker areas still have stuff
on them that the light pressure washing did not remove.

Is there a coat that can be sprayed on to get my roof to be a uniform
color? Thanks.
Ed