# Car taillights -- has the specific "red" color been legally standardized? **URL:** \ **Category:** Factual Questions\ **Created:** [September 15, 2009, 7:09pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209 "2009-09-15T19:09:31Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![Jimmy\_Joe\_Meager](https://avatars.discourse-cdn.com/v4/letter/j/bb73d2/32.png) [@Jimmy\_Joe\_Meager](https://boards.straightdope.com/u/Jimmy_Joe_Meager)\ **Post date:** [September 15, 2009, 7:09pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/1 "2009-09-15T19:09:31Z")
Driving on a busy highway at night, I’ve noticed the oncoming headlights have distinguishable variations in color. While most are “white”, a noticeable percentage (10% or so) have a discernable bluish or even greenish tinge. However, looking at the sea of taillights in front of me… they all appear uniformly the same shade of “red”. While there are occasional outliers (e.g. a botched repair job), I’d estimate those account for less than 1% of the taillights. The other 99%+ are all the same shade of red. (And, as far as I know, I’m not colorblind.) Do you see this too? Mostly “white” headlights, but some bluish or greenish? And taillights… do you find they do not exhibit the same color variation seen in headlights? If so, do motor vehicle laws (federal, I’d assume) indicate a specific spectrum of “red” that must be emitted by taillights? What, then, explains the color variations seen in headlights but not taillights? ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [September 15, 2009, 7:24pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/2 "2009-09-15T19:24:54Z")
The headlights have been changing colors over the years as technology has progressed from brownish plain tungsten lamps, to halogen and now to brilliant blue-white HID or high-intensity discharge designs. Just to confuse things, you can also buy standard halogen lamps with a blue glass casing so they put out bluish light to mimic HID lamps. Some people think they’re brighter, some think they’re “cool” because they give the look of a $900 lighting system for five bucks. Some get pulled over by cops because they’re too blue. (Blue lights being exclusively reserved for law enforcement vehicles.) Tail lights, OTOH, have been plain old little tungsten bulbs behind red plastic all these decades. Only recently have red LEDs been coming into use. Oddly, one factor that holds them back from wider use is durability. Look at the back end of a truck or bus, and you’ll probably see several dead spots in their tail lights. Another hindrance is their cost. ---
**Author:** ![fructose1](https://avatars.discourse-cdn.com/v4/letter/f/f05b48/32.png) [@fructose1](https://boards.straightdope.com/u/fructose1)\ **Post date:** [September 15, 2009, 7:27pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/3 "2009-09-15T19:27:43Z")
I think these questions are a lot simpler than you realize. First off, the red for tail lights: Back in the day, you needed a red filter to make a ‘red’ light. Because there are only so many dyes for plastic, and by now everyone has found which dye and plastic are the cheapest to use, I’d wager to say that most lights that use bulbs are the same color because it’s the cheapest. With ‘modern’ LED tail lights, you are pretty limited to your color choice, and the main ‘red’ colors are only 2 nm apart in [wavelength](http://www.oksolar.com/led/led_color_chart.htm). Good luck differentiating them. For headlights, you’ve got several things going. First is what type of bulb are you using? Is it a halogen light bulb or a normal light bulb? What type of reflector material are you using? Are they clean? A dirty lens will change the color of white light dramatically, but red is only a limited band of wavelengths and can’t change much. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [September 15, 2009, 7:52pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/4 "2009-09-15T19:52:15Z")
Note: Some headlight bulbs are blue for a short time, then are whiter after warming up. E.G., Xenon ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [September 15, 2009, 8:02pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/5 "2009-09-15T20:02:36Z")
> [@gotpasswords](#): > > Oddly, one factor that holds them back from wider use is durability. Look at the back end of a truck or bus, and you’ll probably see several dead spots in their tail lights. Another hindrance is their cost. Hmm. I actually heard this described as their chief advantage for use in things like traffic lights. The array of LEDs can lose a significant number of individual components before the entire thing has to be replaced. Contrast a single-bulb where one bulb failure = immediate need for replacement. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [September 16, 2009, 11:02am UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/6 "2009-09-16T11:02:11Z")
> [@KneadToKnow](#): > > Hmm. I actually heard this described as their chief advantage for use in things like traffic lights. The array of LEDs can lose a significant number of individual components before the entire thing has to be replaced. Contrast a single-bulb where one bulb failure = immediate need for replacement. The main annoying thing with those LEDs is the way they flicker, so on fast-moving vehices they appear as a trail of separate dots. Re the colour question, I’m sure I remember reading somewhere that there was a specified wavelenght range for certian vehicle lights, but I can’t find it now. ---
**Author:** ![Jimmy\_Joe\_Meager](https://avatars.discourse-cdn.com/v4/letter/j/bb73d2/32.png) [@Jimmy\_Joe\_Meager](https://boards.straightdope.com/u/Jimmy_Joe_Meager)\ **Post date:** [September 16, 2009, 1:45pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/7 "2009-09-16T13:45:31Z")
> [@Colophon](#): > > Re the colour question, I’m sure I remember reading somewhere that there was a specified wavelenght range for certian vehicle lights, but I can’t find it now. This is what I was wondering. Turn signals, for example, are usually described as “amber” colored. Why not “orange”? “Yellow”? “Burnt sienna”? Same for “red” taillights. Given the fact that some people like to customize the appearence of their cars, why don’t we see more pink-ish or purple-ish taillights? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [September 16, 2009, 2:09pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/8 "2009-09-16T14:09:43Z")
> [@Jimmy\_Joe\_Meager](#): > > This is what I was wondering. Turn signals, for example, are usually described as “amber” colored. Why not “orange”? “Yellow”? “Burnt sienna”? Same for “red” taillights. Given the fact that some people like to customize the appearence of their cars, why don’t we see more pink-ish or purple-ish taillights? other colors can be confused with lit signage and other lights. for reasons of safety you want them to be quickly recognized. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [September 16, 2009, 2:33pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/9 "2009-09-16T14:33:50Z")
I asked this same question some time back but for some reason can no longer find the thread in a search. Mostly the answer is that there are no legal standards but there _are_ engineering standards. An engineering organization (can’t remember which one now) set a standard for this by specifying the color as a wavelength, IIRC. ---
**Author:** ![Turble](https://avatars.discourse-cdn.com/v4/letter/t/8dc957/32.png) [@Turble](https://boards.straightdope.com/u/Turble)\ **Post date:** [September 16, 2009, 3:46pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/10 "2009-09-16T15:46:44Z")
I think there must be some legal standard for the color of tail lights. I have seen some tail lights (mostly on the souped up 57 Chevy and such hot car types) that look purple from a distance but are the normal red close up. They have a blue marble in the middle of the lens that causes the effect. Can’t say for sure but I have been told they are not legal, at least in some states. ---
**Author:** ![WolfpackJeep](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpackjeep/32/2921_2.png) [@WolfpackJeep](https://boards.straightdope.com/u/WolfpackJeep)\ **Post date:** [September 16, 2009, 4:52pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/11 "2009-09-16T16:52:49Z")
> [@CookingWithGas](#): > > I asked this same question some time back but for some reason can no longer find the thread in a search. Mostly the answer is that there are no legal standards but there _are_ engineering standards. An engineering organization (can’t remember which one now) set a standard for this by specifying the color as a wavelength, IIRC. How about SAE J578 (color specification)? It doesn’t mention wavelength though – it features a chromaticity diagram, with specifications for various colors (red, amber, blue, etc.). ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [September 16, 2009, 5:10pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/12 "2009-09-16T17:10:29Z")
A number of BMW’s have some kind of fluorescent tube in their taillights, which are a noticeably deeper, more intense shade of red than the ordinary incandescents. ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [September 16, 2009, 5:51pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/13 "2009-09-16T17:51:17Z")
> [@Jimmy\_Joe\_Meager](#): > > However, looking at the sea of taillights in front of me… they all appear uniformly the same shade of “red”. While there are occasional outliers (e.g. a botched repair job), I’d estimate those account for less than 1% of the taillights. The other 99%+ are all the same shade of red. (And, as far as I know, I’m not colorblind.) > > If so, do motor vehicle laws (federal, I’d assume) indicate a specific spectrum of “red” that must be emitted by taillights? What, then, explains the color variations seen in headlights but not taillights? I’m not sure I’d agree that they are all the exact same shade of red, you may be over generalizing. From Wiki… > [@](#): > > Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. They may similar enough that they are indiscernable unless compared side by side or bandwidth measured. For them all to be the same there are a number of variables that would have to be equal, such as the bulb’s type, age, colour and intensity as well as the characteristics of the plastic lenses. Of course, the auto parts manufacturers may have settled on a shade of red plastic due to cost, etc.. …or of course someone may have cornered the market on tail lights.:dubious: ---
**Author:** ![Jimmy\_Joe\_Meager](https://avatars.discourse-cdn.com/v4/letter/j/bb73d2/32.png) [@Jimmy\_Joe\_Meager](https://boards.straightdope.com/u/Jimmy_Joe_Meager)\ **Post date:** [September 16, 2009, 6:37pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/14 "2009-09-16T18:37:19Z")
> [@Sparky812](#): > > I’m not sure I’d agree that they are all the exact same shade of red, you may be over generalizing. They may similar enough that they are indiscernable unless compared side by side or bandwidth measured. I’m not ruling out the possibility that my observation may be flawed. Or… Maybe headlights emit light in the part of the spectrum where it’s easier for the human eye to detect very subtle differences. And maybe the “red” emitted by taillights is in a part of the spectrum where the human eye isn’t as sensitive to very slight variations. Anyone know? ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [September 17, 2009, 12:51am UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/15 "2009-09-17T00:51:10Z")
Here in Minnesota, there is certainly a legal requirement to have only red taillights. I’ve had friends stopped & given a ticket for having non-red taillights (white, where the red plastic cover had been broken off). Nice cops gave them a 10-day fix-it ticket. Mean cops gave them an actual $74 ticket. ---
**Author:** ![JRDelirious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jrdelirious/32/9531_2.png) [@JRDelirious](https://boards.straightdope.com/u/JRDelirious)\ **Post date:** [September 17, 2009, 1:20am UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/16 "2009-09-17T01:20:37Z")
I also vote for the range of variation while still being “red” being narrow enough that it’s undistinguishable for most people in normal conditions. My question is why the apparent move away from orange rear turn-signals back to red-on-red, even on foreign makes of cars (used to be for a while it was American cars who had kept red-on-red, everyone else seemed to go to red-brake + orange-turn) ---
**Author:** ![Chickenwrangler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chickenwrangler/32/91_2.png) [@Chickenwrangler](https://boards.straightdope.com/u/Chickenwrangler)\ **Post date:** [September 18, 2009, 3:32am UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/17 "2009-09-18T03:32:48Z")
In the UK there are British Standard Colors that I believe cover car lights so all shades of vehicle lights are the same. This would apply to practically everything including traffic lights and hazard yellows. [http://en.wikipedia.org/wiki/British\_Colour\_Council](http://en.wikipedia.org/wiki/British_Colour_Council) ---
**Author:** ![Jimmy\_Joe\_Meager](https://avatars.discourse-cdn.com/v4/letter/j/bb73d2/32.png) [@Jimmy\_Joe\_Meager](https://boards.straightdope.com/u/Jimmy_Joe_Meager)\ **Post date:** [September 18, 2009, 2:10pm UTC](https://boards.straightdope.com/t/car-taillights-has-the-specific-red-color-been-legally-standardized/510209/18 "2009-09-18T14:10:40Z")
**Observational update** Driving home last night I made a point of looking at taillights from different distances. No, they’re not all \*exactly \*the same shade of red. However, I noticed that I could generally only tell the difference very close up, e.g. stopped at a stoplight when two cars were literally right next to each other. The further away they were, e.g. several hundred yard ahead on the highway, the more they all looked the same. ETA: However, taillights still don’t exhibit the variation seen in headlights. That is, blue-ish and green-ish.