For reasons I do not need to go into here except to say on commercial jobs I tell electricians ignore colors and use a rotation meter, I would tell the DIYer.
IGNORE colors with the exception of green, white (In most cases) jacket color has no meaning use and may vary from manufacture to manufacture. LOOK at the conductor size and as DIYers I would rely on the actual AWG number on the conductor jacket, not on your ability to assume the size by visual inspection.
While rummaging around in 210.23, I see they define "Cord-and-Plug-Connected Equipment Not Fastened in Place" and "Utilization Equipment Fastened in Place". How would you treat Cord-and-Plug-Connected Equipment Fastened in Place, such as a wall-mounted hair dryer? It would seem that the fastening-in-place is what matters, but that would mean my 1500W wall-mounted hair dryers couldn't be plugged into 20A receptacles on circuits where an electric toothbrush, say, was also plugged in. 210.23(A)(2).
I only read the quotes I posted here.What exactly are you confused on? Did you read the exception?