In the diagram on the link they are using a three conductor cable after the first three way switch. Black, Red, and White with a separate ground.

A three-way switch has three screw terminals on the body of the switch in addition to the green grounding screw. One screw, known as the common, is a darker color than the others.

Below, Donnelly tells AD how to wire a light switch with this simple step-by-step process for a single-pole light switch without zapping yourself along the way. To make the task easier, Character ...

On a smart switch, the red wire often connects to the switch leg to control a light or other load. Within an electrical box, a red wire may be a traveler, a switch leg or the second hot of a 240 ...