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 '12 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 '12 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 '12 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 '12 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 '12 at 17:36

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 '12 at 1:12
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    ... and running it is called "squeezing the lemon."
    – fortunate1
    Sep 18 '12 at 1:22
  • @Malvolio: That's also the case in the UK Highway Code. For several reasons I suspect proportionately more Americans "run" traffic lights than Brits do. A former first lady comes to mind. Sep 18 '12 at 1:23
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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 '12 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 '12 at 9:39

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.


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.


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.


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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