I did my own roof and it turned out grest, after 5 days I took my hose and sprayed my roof close to the siding under the eaves where the lower roof meets the taller part of the house and I noticed that area turned lighter than the area that was not rinsed, why would this happen?
If it's been five days with no rain, the rest of your roof han't been rinsed yet. Therefore there is still dead algae and dirt on those areas and it will be darker than the clean area you rinsed.