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What receptacle unit colors indicate their intended uses? Research taught me:

  • Red receptacles are used by hospitals to indicate the circuit has backup power like UPS or generator, and also to make them easily identifiable to doctors and staff.
  • Orange receptacles are used to indicate it's an isolated ground receptacle, useful to remove humming and noise. Orange with green dots indicates it is hospital grade.
  • Blue receptacles units are used to indicate it has surge suppression and protection against transient voltage spikes, and that they have three levels of surge protection.

But what about black, brown, and gray receptacles? I know we can use any color unit anywhere in and around the house as we please, but I've always seen grey receptacles used outside, and black receptacles used in garages. I think I heard a black receptacle with a white cover plate may indicate something else. Or are they purely aesthetic and don't indicate what or where they're used for?

Note: I am not asking about wire colors or decorative preferences.

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    It would be better to use the term "receptacle", the NEC definition of "outlet" includes light fixtures and other hard wired points of attachment.. Jan 14, 2023 at 2:46
  • Counterpoint: I teach in a workshop where there are both red and white power sockets. Red ones are on a circuit with emergency stop plungers, to interrupt the supply to experimental equipment in case of an accident. The white sockets are regular circuits for PCs and the like, but with no UPS provision.
    – Kaz
    Feb 3, 2023 at 21:51

3 Answers 3

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Purely Aesthetic, unless they have been designated to serve a purpose locally (generally meaning building level locally.) Even the ones you list are conventions, albeit largely enforced in practice by the high price of "odd colors" relative to the usual ones. Isolated ground should have a triangle, otherwise it's just an orange receptacle, and non-orange ones are made.

NEC 406.3(D) Specifies that isolated ground receptacles shall be identified by an orange triangle on the face of the outlet.

One place I often do jobs in has orange non-isolated receptacles to indicate backup power, not red. Red is often associated with fire alarm related circuits.

Likewise, "Hospital grade" has a green dot, and can be any color. Quote from: https://code-authorities.ul.com/wp-content/uploads/2014/04/ul_HospitalGradeReceptacles.pdf

Hospital grade receptacles include the same markings that appear on general use receptacles, and also include “Hospital Grade” or “Hosp. Grade”, typically on the back of the receptacle where visible during installation. A Green Dot is provided on the receptacle face where it is visible after installation with a cover plate secured.

While it's often done as just decor, you certainly can use receptacle color to help identify what leg of the service an outlet is on, or what circuit the receptacle is on in a room with multiple circuits. There's no "official convention" for that, however. And the affordable colors limit the extent of that for normal-budget people.

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NEC does not call out any standard here.

The manufacturers like to make a type of socket called "Hospital Grade" and they are built better than spec-grade outlets. But that's just marketing.

Other than that, special colors are generally decided by the individual site.

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Many hospitals have standardized on a Red, Orange, Blue, (and White) receptacle color scheme, with red being the standard for generator backed power. While such a scheme is common and useful, I am not aware of the colors of the receptacles being covered by a specific code.

Outside of hospitals, the likelihood that the colors are applied consistently is small. For example, I once lived in a home with a single black receptacle, years passed until it was serviced, and the electrician indicated it was nothing special. I also lived in a home with a red receptacle, that clearly lacked generator power (we guessed that the prior installer just used it because they had a red one handy).

However, when we had an electrician rewire an in-office server room for generator power, they were happy to do so without changing the receptacles, and we had to specifically request and install colored receptacles. Since we saw the hospital standards, we opted for red ones, but due to sourcing issues, we didn't get the full red receptacle with red plates, so we have red receptacles with white plates.

All of these are anecdotes, in a relatively small region of the USA. Check your local codes for better answers; but, these anecdotes imply that a national code doesn't exist for the USA.

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