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What is the difference in usage between amber and yellow, when it is the color of traffic lights or some derived meaning? Is this purely a difference between British English and American English, or does the context matter?

For example, on each side of the Pond, if you're driving, is it an amber light or a yellow light that announces an imminent red light? When indicating a status between red (no go) and green (ok), is the status amber or yellow?


EDIT: I already know that the UK has amber lights and the US have yellow light, this is not what I am asking here. What I am asking is whether there is more to it than a simple US/UK distinction. How unusual would it be to use the wrong word? Is the usage for traffic lights the same as for derived meanings such as traffic light rating system? What prompted this question was finding that the Wikipedia article on the rating system uses amber — I don't know if this reflects US usage as well, or if this is merely due to the article having been written by a BrE speaker, or if the RAG rating is a purely British notion and AmE speakers would not think to use a red/yellow/green rating system.

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    Here in the U.S., I usually hear it referred to as yellow, although I have heard amber on occasion.
    – J.R.
    Sep 18, 2012 at 0:19
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    In the US, the in-between light is called 'yellow'; 'amber' is fossilized sap that ancient insects are embedded in.
    – Mitch
    Sep 18, 2012 at 1:17
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    @Mitch There's more to amber than 'fossilized sap that ancient insects are embedded in'.
    – Kris
    Sep 18, 2012 at 13:52
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    Note that in the US, the traffic light sequence is green - yellow - red - green. I don't know about the UK, but in the parts of Europe where they drive on the correct side of the road, the traffic light sequence is green - yellow - red - red+yellow - green. Not that any of this makes any difference to what that middle light color is called, mind you.
    – Marthaª
    Sep 20, 2012 at 16:56
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    @Marthaª Not in all the parts of Europe: some have the same sequence as the US, some go G-Y-R-Y-G (yes, the yellow is ambiguous), and there are more variations such as flashing. See Wikipedia for an incomplete list. Not that this is relevant to my question, so we shouldn't be having this question here. Sep 20, 2012 at 17:36

6 Answers 6

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I'm not sure I've ever heard of yellow traffic lights, but here are 65 written instances of "drove through a yellow light".

I assume it's a US/UK difference. To my British ear, "drove through an amber light" sounds natural, but there are actually only 7 of them.

Note that "ran a yellow light" gets 369 hits, against 23 for "ran an amber light". That stronger bias I put down to the fact that ran a red light is about ten times more common in the US than the UK.

I doubt anyone's choice of colour-word would be influenced by the exact wavelength/frequency of the lights themselves on either side of the Atlantic, but it's worth noting that the UK sequence is Red, Red and Amber, Green, Amber, whereas in the US it's just Red, Green, Yellow. The colour amber is often described as a reddish or brownish yellow. Perhaps British usage is influenced by the fact that half of all the times we see our "yellow" light, the red one is also on.


The official British "security alert" scale was headed by red, amber until it was replaced in 2006 (by an apparently non-colour-coded scale). The American equivalent has red, orange (yellow next).

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    In the US, the law calls it an amber light; the drivers call it a yellow light, or just a "yellow". Sep 18, 2012 at 1:12
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    ... and running it is called "squeezing the lemon."
    – fortunate1
    Sep 18, 2012 at 1:22
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    It's all a matter of dialect. When I was a kid in the USA back in the 1950s, traffic signals had red, green, and {amber / yellow} lights. Mid-Atlantic dialect (northern and central New Jersey). California calls these lights yellow link; New Jersey does too link.
    – user21497
    Sep 18, 2012 at 2:51
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    Unlike the obvious alternative, the slogan 'Don't be a yellow gambler!' has never really caught on over here in the UK. Sep 18, 2012 at 7:48
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    @Billy That's surprising. When I grew up in the UK, I consistently heard the word "amber". In fact, I knew that the word "amber" meant "the colour of the middle light in a set of traffic lights" long before I knew that it also referred to a kind of fossilised resin.
    – Pitarou
    Sep 18, 2012 at 9:39
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Amber and yellow are two different colors, technically.

Yellow is one of the CMYK primaries (0,0,100,0), while amber has a bit of magenta in it (0,25,100,0). On the color wheel yellow is at hue 30 and amber at 45. RGB values are 255,0,0 for yellow and 255,191,0 for amber.

In LCH space, which encodes perceptual brightness (L), chroma (C, richness) and hue (H), you can see that yellow is brighter than amber (L=97 vs L=81) and richer (C=86 vs C=57).

It turns out that there is a different definition of amber (SAE/ECE amber) when it comes to turning lights for cars. This amber is at RGB 255,126,0 which puts it even darker (L=66) and murkier (C=29) than the amber defined above.

There are some car lights that are strongly yellow (fog lamps). For these selective yellow is used.

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  • Those really are just labels that we chose to give those parts of the spectrum though and different regions often assign the label up and down the spectrum. In addition the poster is using "light" as an example... and the subtractive CMYK model isn't usually applied to light, bur rather the additive RGB model is, instead.
    – OneProton
    Sep 1, 2022 at 16:28
  • Good answer - And it allowed me to have my morning coffee without having to type. I'm a former SAE committee member.
    – Phil Sweet
    Apr 11, 2023 at 9:34
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For what it's worth, in the US military, the status of things like communications, logistics, or tasks are referred to as Green / Amber / Red. For some reason, with that background, I call the lights on a stop light Green / Yellow / Red but any similar status updates in the civilian world I still use Green / Amber / Red.

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In the U.S. the DMV and DOT classify the traffic light as yellow and any light on a vehicle that signals caution as amber. Certain instances require obtaining an 'amber light permit'

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We have 1868-2019: A Brief History of Traffic Lights, which says that the first traffic lights were not coloured but were based on a gas-illuminated semaphore system. They were introduced in London 1868 and exploded less than two months later. This consigned them to the rubbish heap of history until…

In 1914, red and green electric traffic lights were installed in Cleveland in the United States. Detroit and New York added yellow between red and green in 1920. The traffic lights that we now know were born and became the norm throughout the world.

[…]

Standardization and Regulation in the 1930s

The first Convention on the Unification of Road Signals was signed in Geneva on March 30, 1931. Its goal was to increase road traffic safety and facilitate international movement by road through a uniform system of road signals. The majority of signs that we recognize today were defined through this treaty. Traffic lights with three colors (red, yellow, green) became the standard.

The original Convention on the Unification of Road Signals is available on a Swiss site in French, Italian and German only:

A. Signaux marquant une interdiction

Dans ces signaux, la couleur rouge doit prédominer nettement et faire ressortir la forme générale du signal. Les autres couleurs sont facultatives, sauf les prescriptions indiquées ci-après:

a)

Circulation interdite à tous véhicules: Disque rouge avec partie centrale circulaire de couleur blanche ou jaune clair (figure 1 du tableau II);

French, German and Italian do have the adjective and noun “amber” but

French uses “jaune” = yellow

German uses “Hellgelb” = light yellow

Italian uses “giallo chiaro” = light yellow

It is clear that, as white did not catch on, according to the convention, the colour is yellow, and only yellow.

The British Highway Code was first published in 1931 and makes no mention of the colours of traffic lights.

The British English version of “The Consolidated Versions of the Vienna Convention on Road Signs and Signals, the European Agreement supplementing the Convention and its additional Protocol, Part I: Convention on Road Signs and Signals Chapter III Traffic Light Signals, Article 23, Signals for vehicular traffic states

An amber light, which shall appear alone or at the same time as the red light; when appearing alone it shall mean that no vehicle may pass the stop line or beyond the level of the signal unless it is so close to the stop line or signal when the light appears that it cannot safely be stopped before passing the stop line or beyond the level of the signal.

The USA, Canada, Australia, New Zealand and South Africa are not parties to this convention.

It thus appears that “amber” is a British English term and, in general, the rest of the world uses “yellow”.

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Regarding Project Management. You can have a RAG status (Red, Amber, Green) but in speaking terms, everyone refers to a project as being "Yellow" if certain risk/issues exist.

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