Had a little house under a big swamp maple,light green mold,distinct from moss,not only the roof shingles but the crappy vinyl siding as well.

We use Tri sodium phosphate,{available in powder form in Home Despot and other venues}mixed with equal amouts of bleach.

TSP comes in crystal or powder form so you mix it to a very strong solution with water,add the bleach and pour it into the tank of a good pressure washer {or wide pattern sprayer}set down for say,60-80 psi.

Did the trick for me. Of course I had to rinse the residuum off with clean water several hours afterwards.