Yorkshire Dave
Western Thunderer
I fully agree regarding pollution and mosses, Dave, but there is always that background natural growth of algae and other species that will out, even in the harshest environments. The effect on the buildings is quite noticeable, they look like representative models before the treatment, afterwards they look part of a scene. The dark green is actually pretty subtle, almost like an ‘invisible green’ and I doubt that anyone would notice unless it was pointed out.
I agree about the algae growth and other species.
You'll have to prepare a 'spot the difference' piece to see if anyone notices. As you say, it's amazing what a sublte wash of green does and it's one of those washes which appears when seen in a certain light or from a certain angle. Green is one of the permanent colours on my weathering palette.