Why does the the peppered moth that lives in the countryside have pale wings?

The peppered moth already existed as darker (black) and lighter( white) forms.

Before the industrial revolution, the tree barks' had lichens which were lighter in color and the surroundings were lighter in color too. This provided good camouflage for the lighter colored pepper moths which gave a better chance to survive than the darker ones. Yet few darker ones survived too probably due to the possession of traits which helped them escape predators.

But after the industrial revolution, due to pollution the lichens which are sensitive to pollution died. In addition the buildings were covered with soot. This provided camouflage and better survival and reproduction to black pepper moths than lighter colored pepper moths. Hence the black pepper moths increased in number than the lighter colored ones.