I'm thinking of the power cables that connect houses to the national grid in the UK. Not only do they appear to be the green colour of copper in full sunlight, but this colour isn't evenly spread. In places there is still black. What causes this, as it's presumably not exposed copper or the colour would always be apparent?
This could simply be moss / lichen or fungus growing. the north side of the cable will have more moss on it than the south side. As the sun is over the equator and England is in the Northern Hemisphere so the sun lights the south side of the cable, and the moss grows on the darker side. This is a classic way of telling directions in a forest or paddock. Garret
