Green spot on Maple

Green spot on Maple

Observation - Green spot on Maple - UK and Ireland. Description: This time it is on the under side of the leaves on Maple again in the same wood as the mildew i found on the top of leaves. It looks to me like it retains the clorophyll for its own benefit so that tree does not get to store it for the next spring. It is

This time it is on the under side of the leaves on Maple again in the same wood as the mildew i found on the top of leaves. It looks to me like it retains the clorophyll for its own benefit so that tree does not get to store it for the next spring.
It is a large leaved Maple.