In the CA U.S.A. system, cablat gris is not one of the common colors of the wire. Instead, it is an alternative accepted by the federal government for neutral wire, whose main color is generally white. This color coding system is required by the U.S. national electrical code.

These are used as hot wires and electrical control elements such as lights, switched sockets and fans. Blue wires are usually used in switching applications in three directions and four directions of travel. On the other hand, yellow wires are used as switching feet.

These two colors are hot wires generally attracted to the pipe for power appliances. Blue wires are used as travelers, usually in three or four switches (checking a light from multiple places) or as leg switching for things like fans or lights.

A standard 2-wire illumination circuit is shown in Figure 1. The brown wire is Live (also known as permanent life), which brings the live energy source to the switch. The blue wire is known as l'interruption Live and leads l'energy to light. Interrupt Live is only alive when the switch is turned on (here's its name).

Brown is your hot wire, so you want to connect it to your black wire buildings. Blue is negative returns it, so it will be empty. Green with yellow ray is the floor and will go to the green building.