Before changing an outlet, light switch or any line voltage wires it is crucial that the power has been completely disconnected from its source (either the breaker box or another source such as an APC transformer). A voltage meter or tester should also be used to verify there is no current flowing through the circuit you will be working on. Once power has been turned off and no current running through it can begin working on it; once power has been completely disconnected you can begin your task but when faced with a complex web of different colored wires it can become confusing trying to figure out what each color represents before diving in head first!
At home, standard line voltage wiring typically uses plastic-sheathed cable that contains three insulated conductors in three colors - usually black and white - with black being considered "hot", while white typically serves as the neutral wire and should only be handled if marked by red or black tape as being "hot"; working on unmarked white wires (unless ribbed or marked red in its insulation ) could prove dangerous as these may contain excess electricity which must return back to the breaker panel and should therefore not be handled due to possible "hot" currents contained therein!). Note: it is wise not to work directly on white wires not marked by red/black tape, since these may become potentially "hot".
Orange and brown are among the more frequently seen electrical wire colors used for three-phase services, while pink and violet may be suitable for travelers or dimming control wire for lights in certain applications. While not typically considered "hot", these wires should still be treated with caution as they can carry electrical current.
