When did color-coding NM-B cable become standard in the US?

Question

Wandering through the electrical aisle of my local big-box store, I see that it is now basically impossible to buy NM-B cable that doesn't adhere to this color coding:

• 14 AWG = white jacket
• 12 AWG = yellow jacket
• 10 AWG = orange jacket

I understand the color coding, and it makes a lot of sense (I've got a mixture of 12 & 14AWG NM-B in my house and I really wish it was that easy to identify which was which when looking in a box). My question is two-fold:

1. When did this become standard (in the US)?
2. Is it an NEC requirement, or is it just a "standard" or "new tradition"?

Answer 1

Type NM-B cable first began to be manufactured with color-coded jackets in 2001 to aid in identification of the conductor size. The color code that was introduced, which continues to be used today is as follows:

• 14 AWG – White
• 12 AWG – Yellow
• 10 AWG – Orange
• 8 AWG – Black
• 6 AWG – Black​

This color coding system was developed to aid those who sell, install, and inspect Type NM-B cable so that the cable size can easily be identified, to reduce mistakes resulting from the use of an incorrect conductor size.