In a three-way switch, two screws are the same ... If you do have this wire, Donnelly says to attach it to the green screw, which will be on your light switch. Reinstall the switch in the junction ...

My house was built in the 50s, with wiring ... modern switch is 2 blacks marked hot, a white marked neutral, and a grey marked gnd. It seems like maybe the existing switch is a 3-way switch?

And few electrical projects are as simple and safe as replacing an old light ... the wire until it releases from the switch. Once you’ve disconnected all the wires, bend them out of the way ...