Green electrical plugs?

This is a type of corrosion. It is in fact rust. When copper rusts it appears green. So when you stick a plug in there it's picking up the rust and spreading it around.

One factor might be that you have an excessive humidity level.

Your going to need to replace, as in get rid of any contaminated surface. Unfortunately this maybe the sockets, or something that is plugged into them.

It wouldn't be a bad idea to get the help of an electrical contractor.

As a radio engineer it was often discovered that antenna cables were getting this rust that creeps up inside the wire. The only solution was to cut off the effected area, and make sure the replacement were sealed.

If you mean from the green sulfate metal erosion ,there must be moist or water leak in that section ,now leak from roof or leak from pipe .If color of the plastic cover of plug it turn to green that may cause of the material used in plastic that during heat it turn to green color .

That sounds like some kind of corrosion going on. Whatever it is, it's not good.

If you're lucky, you've got a leak somewhere and water is getting behind the walls.

If you are not lucky, your house was built with high sulfur content gypsum board (drywall), imported from China. See my source, below.