I keep finding pins on old motherboards that are designated "Green LED", "Green PC LED", "Green switch", "Green PC switch", "Green connector" and "Green PC connector".

Can anyone tell me what are they for? Google failed to give me a valid answer, and so did the Wikipedia.

The first ones will be for the power LED on the case, HDD activity light, power switch and reset switch I'd imagine. Not sure about the last 2, though.

Nope. The LED connector is labeled as "Green LED" or "Green PC LED", the other four names are different variants I encountered on several motherboards.

Power LED/HDD LED/Reset switch all have named connectors assigned for them, and Power switch is not taken into account, since all these motherboards are ye olde AT.