I have seen this green liquid directly at the outlet. Example: basement GFI outlet, 4 feet above floor level, mounted on an interior wall, copper wires in conduit feeds the outlet from above. The basement is dry and has never flooded. The basement sump pump plugs into this outlet. When you unplug the pump, there is noticeable quantity of bright green "gell" on the female GFI sockets and on the male plug. I realize that copper turns green when exposed to moisture, but this "green jello specs"? I have seen this in several basements.
I have been assuming that this is copper oxidizing onto some contact grease that the GFI people put on the female contacts. But I really don't know.