The jacket colors of Romex are standard because they are stocked at the factory. The only way to get a Romex cable in a different color jacket is to place a special order with a minimum quantity which youll be able to see in about 5 to 6 weeks. Southwire owns the brand name of Romex and will give a minimum of at least 30,000 feet in order for them to take off the standard product to manufacture a special cable.
NMB cable is the same type of cable but Romex is a brand name that has slight differences to the standard NMB cable. Both types of electrical cables have the same approvals and color codes though. The 14 AWG cables come in a gray jacket that identifies it as a 14/2 cable or a 14/3 cable. Both would also come with an additional ground wire.
Romex 12 AWG cables come in a yellow jacket to identify them as 12/2 or 12/3. The difference between the 12/2 and 12/3 is the amount of conductors. The 12 means 12 AWG and the 2 or 3 designate the amount of THHN wire inside the cable. Remember that the ground wire is always extra so it would be a third or fourth wire as a bare copper ground.
NMB 10 AWG cables come in an orange jacket to identify them as 10/2 or 10/3. Having these cables with color coded jackets helps the electrician, contractor or installer automatically identify they cable without having to cut it open or rely on the faded printing on the jacket.
The balance of Romex cables come with a black jacket. They range from 8 AWG through 2 AWG in a 2 or 3 conductor count. All of the NMB cables have THHN wires as their conductors and a bare copper ground wire. You can request different inner conductors but it will most likely result in buying a different type od standard cable. Many requests are geared towards the amount of flexibility the cable has.
Speak to your supplier about the cable youre going to run and the environment that it will be running in. That way the supplier can help you find the cheapest version of what you need with all of the approvals needed to pass inspection. Analyzing it your self can result in buying a more expensive cable than what you need or possibly buying the wrong cable all together.