We can see lots go colors in one PCB, and sometimes we may get confused about them. Here, EPCB lists some common wire colors, and wish it is useful for you. In a circuit, the main load wire — the live power wire between the switch and power source — is typically black, and the secondary load wire is usually red. Wire colors can vary between circuits, so it is best to remove or turn off power sources before touching them. A yellow and blue striped wire may also be used for power in a circuit, but only in applications that don't require the heavy-duty demands of a traditional wall power outlet. Other colors that may appear in a circuit include green wires for grounding and gray wires for neutral portions of the circuit.