12 guage wires with yellow casing?

When did they start using yellow to identify 12 gauge wires?

Although it’s not required I think that it’s been around for about 8-10 years. I believe that Southwire was the first to use the current standard of White-#14, Yellow-#12, Orange-#10 and Black-#8.

Thanks, I was just starting in construction as a college student back in the early 2000s and it already had quickly become the standard. While I was investigating excessive voltage drop today, someone wanted to know why a house built in 2000 did not have yellow wiring for the 12 gauge circuits.

Can I assume you are talking about the jacket of Romex or NM-B?


The yellow is not a required color coding. The cables could have been new old stock and was being used up.