As a professional electrician, we have a saying. "Never trust colors without verifying with your meter". A good example of when relying solely on the color can lead to dangerous mishaps, is in residential and some commercial systems when supplying a 240 or 208 volt circuit to equipment that doesn't require a neutral, such as a large air conditioner or electric water heater; for such equipment it is a common and code compliant practice to use a two wire with ground cable such as NM or MC containing a black, white and green or bare wire. In this situation the white is being used as the secondary hot (aka ungrounded) wire and is required to be re-identified as such, usually by wrapping it with a piece of electrical tape near all terminations. Unfortunately this isn't always done in older systems or when installed by unqualified handyman.
As a professional electrician, we have a saying. "Never trust colors without verifying with your meter". A good example of when relying solely on the color can lead to dangerous mishaps, is in residential and some commercial systems when supplying a 240 or 208 volt circuit to equipment that doesn't require a neutral, such as a large air conditioner or electric water heater; for such equipment it is a common and code compliant practice to use a two wire with ground cable such as NM or MC containing a black, white and green or bare wire. In this situation the white is being used as the secondary hot (aka ungrounded) wire and is required to be re-identified as such, usually by wrapping it with a piece of electrical tape near all terminations. Unfortunately this isn't always done in older systems or when installed by unqualified handyman.
Good video 💯
In telephony, wire color often with two or even three colors, like black-yellow or red-green, as well as many others.
Fun fact: My stepdad complained that a house that we bought had wires that were all the same color and wired with almost no safety measures.
first knew this though