Why the colours we use (Brown/Blue/Green+Yellow)

The electrons do not care - but we do as it makes it easier to remember what is going on. (*)

Well, colours have changed many times in the past, and may well do so again. In the UK green was earth after the war (earth was black pre-war, if it was there at all, and green was 3rd phase, so live in some installations of that era) and earth became stripy in 1970 - and this was coordinated across the EC as it was then - previous there were many national standards - as an example of the problem, in Germany black was a live colour, and red was reserved for earth, as earth is a really important safety thing, to them making it red seemed like a good idea.

Actually Red for earth was also used in Switzerland and parts of the soviet block as well.

But stripy looked like nothing else and was accepted almost immediately. There is also an advantage for colour-blindness, that the stripes of something light and something dark are still unique.

The UK 'red for live' and the German red for earth meant that sensibly red had to go. So brown - a bit like the German black, and a bit like the English red, but not easily confused with either became the new live on single phase flexibles.

However, in the UK fixed wiring stayed with red and black until 2004 - arguably as it does not get moved around like portable gear and is unlikely to be opened by someone unfamiliar with local regs it was not seen as a priority.

Now (post 2004) we have got used to the flex colours and the fixed cable colours being the same

Live 1 brown

Live2 Black

Live 3 light grey

Neutral blue

stripy green yellow earth.

Mike,

* well not always. sometimes you find things like 3 phases, with a live on brown, a live on blue and a live on green yellow. At this point a multi meter and some nerve  is needed to sort out what is happening. 

And our idea of standard colours is by no means universally accepted - look at the pics in this thread to worry yourself about practices in Baku, Azerbaijan   here 

Later edit actually the pics have not survived the forum re-shuffle , so here is one.  Note the use of green and yellow for a 3 phase supply, as well as for earth/neutral , and blue for the meter wires as well... oh and the open live terminals at the bottom.

Even in the UK there's been right mess of colour codes over the years- e.g. see https://electrical.theiet.org/wiring-matters/years/2021/84-march-2021/the-history-of-colour-identification-of-conductors/ and our continental cousins hadn't really got the harmonized thing properly sorted until recently either (L was typically brown or black, but which indicated L1, L2 or L3 was still a bit random) see - https://electrical.theiet.org/media/1720/harmonised-colours-and-alphanumeric-marketing.pdf

Little surprise then that the recent introductions have picked much less common colours (e.g. grey and pink).

I think the modern colour codes actually come from IEC (i.e. worldwide) standardization, and merely adopted by CENELEC (not the EU) so have had to consider American and other practice too (e.g. white for N to match the tin plating they put on N terminals for identification).

   - Andy.

The great merit of green/yellow striped for earth is that it is obvious even to someone with defective colour vision that the striped one is the earth.

Normal colour vision is a requirement for performing most types most types of electrical installation work, however a colour blind householder might need to wire a plug.

Knowing that the striped wire is the earth is a potential lifesaver in such circumstances. Confusing the live and neutral does not much matter when wiring a plug. Remember that many countries use reversible plugs and sockets, so polarity at a portable appliance is random, and no one worries.

"Normal colour vision is a requirement for performing most types most types of electrical installation work" Why then is a colour blindness test (or even a question about it) not a requirement under the various schemes?

PS there are plenty of colour blind electricians

Complete inability to perceive colour is rare. Red/green is the commonest type, so that shouldn't be a problem with reasonably modern installations. Even then, it should be obvious whether a conductor is line or earth fron the way that it is connected.

Colour-blindness isn't exactly going to make any difference with grey and black conductors.

Would-be Royal Navy engineers who fail the normal tests have to undertake trade tests to demonstrate that they will be able to identify what they need to.

Also, to add to the history, a change was made to the identification colours for L+ and L- conductors for DC systems, and also to the identification for FE (functional earthing) conductors. The latter was explicit in Corrigendum:2018 (the former inferred by implying an implementation date for BS EN 60445 in the Corrigendum also). The Draft for Public Comment for Amendment 2 to BS 7671:2018 saw these changes in Table 51 itself. Further information in this article: https://electrical.theiet.org/wiring-matters/years/2020/83-november-2020/section-514-identification-and-notices-in-the-amendment-no-2-draft-for-public-comment/

gkenyon said:

Further information in this article: https://electrical.theiet.org/wiring-matters/years/2020/83-november-2020/section-514-identification-and-notices-in-the-amendment-no-2-draft-for-public-comment/

The small label for surfaces <10cm² is a curious one - since the label itself appears to be 12.5cm² (5cm wide x 2.5cm high).

  - Andy.

My feeling has always been, why they changed the colour system, was because they can! I guess someone said oh dear... lets upset electricians' BUT HOW? Ah!! Lets throw our weight around and change the RYB to BBB. Someone probably won an award for it, somewhere!

No, they changed it so that many countries could then all use the same scheme. You can of course debate whether the pain of transition was worth the gain of harmonisation, but there was a real motivation for it, not just "because they can".

Now there speaks some-one who has never worked abroad  or had to interface to local electrics there. Standardization of colours between countries has slowly reduced things like incidents of shocks and destroying containerized equipment by mis-wiring it when it arrives in country.

My father saw a  colleague killed in about 1970 by a UK sparks putting a UK plug on a German submersible pump and assuming red was live and black was neutral - having cut the Schuko plug off and thrown it away he just put a UK plug on it assuming the UK use of the colours. The unfortunate colleague picked it up and walked into a salt water tank with it to put it in position, and then after a cheery wave to do so it was switched on...

Mike