The type of NM cable approved for indoor (dry location) use is NMB cable, and a color code for the plastic cable sheathing has been an industry standard since about 2001:

White - #14 AWG  (rated for maximum 15 amps)

Yellow - #12 AWG (rated for maximum 20 amps)

Orange - #10 AWG (rated for maximum 30 amps)

Black - #8 and larger (higher amperage ratings - not shown above)

Gray - UF (Underground Feed) means cable rated for exterior use but color does not indicate wire size. Wire size printed along sheathing.

    Color coding makes it easy to identify wire size in the cable at a glance but the National Electrical Code (NEC) does not require it. The NEC does, however, require that wire size be imprinted in the repeating data strip running along the sheathing. 

    The wires inside the sheathing are also color coded, as shown below. NM-cable for a 240-volt circuit will also have an additional hot wire that is red. 

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Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:

• What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?

• Why is it unsafe to bond neutral and ground wiring at subpanels?

• Should I get a lightning rod system to protect my house?

• Why is a strain relief clamp necessary for the cord connection to some electric appliances?  

• Does a wire nut connection need to be wrapped with electrical tape?

• What is the minimum clearance of overhead electric service drop wires above a house roof?

• What are the requirements for NM-cables entering an electric panel box? 

• What is the color code for NM cable (Romex®) sheathing?

• Why is undersize electric wiring in a house dangerous? 

• What causes flickering or blinking lights in a house?

• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

• How can I find out the size of the electric service to a house?

• Can old electrical wiring go bad inside a wall? 

• What is an open electrical splice?

• What are the most common electrical defects found in a home inspection? 

• What is the life expectancy of electrical wiring in a house? 

• What is an "open junction box"? 

• How dangerous is old electrical wiring? 

• What is a ground wire? 

• I heard that aluminum wiring is bad. How do you check for aluminum wiring?  

• What is "knob and tube" wiring?  

• What is the code requirement for receptacle outlets in a closet?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.