Gold

The HQ building of Shell Aberdeen. They have been here since oil was first discovered off the coast in the North Sea. They have probably taken out more than they have given, although I cannot really complain, as they do give an awful lot of work to the taxi company I work through.
Here, in the sunshine, the windows shine like gold.
But at night, when the offices are empty, they are just black.
Ironic as oil is black gold.