I've seen various models with blue-shifted LED headlights. Most notably, Toyota and Tesla. I have a photo on my phone somewhere.

Has anyone else seen such a phenomenon? I assume it's the same phosphor detachment from high ambient heat suffered by some earlier LED streetlights?

I have seen the same thing. Usually I don't see the purplish-tint associated with partial phosphor detatchment, and usually I don't see the ~monochromatic blue associated with complete phosphor detachment. I always assumed it was just different color headlights that you could get (10,000K blue for example). But of course I could be wrong.

On the rare occasions that I do see purple, that can be at least partially explained by the availability of 12,000K headlights, which are purple-ish in color. Or it could of course be partial phosphor detachment.

Never heard of phosphor detachment in headlights, but I am sure it is possible. I guess the color could be either from that or from the driver's color preference. Can't really know which one without closer physical inspection though (or using a spectrometer maybe).

Very interesting, I haven't seen that here, and I do pay attention to cars. I presume the Toyotas and Teslas in the USA are locally made, but I've got no idea about the lights...

I am trying to find the crystal-clear photo I took of a ~2020 Model 3 with this phenomenon. I was standing next to him at a light and managed to capture both the good and bad headlight side by side. While he was driving (one lane road, two or so cars ahead), you could see the bluish-purple UV-colored cast on the surrounding roadways and tree trunks. Unfortunately, my phone is not "tagging" these photos on the map (particular location), and nor are they showing up in my gallery's "Enhanced AI Search". I also do not remember the approximate time of year I took them... all I know is "2025, particular roadway that I take every Tues and Thurs evening to piano." 

Reason why I made this thread was because I noticed a similar, albeit less severe case of this on a 2023 Toyota Corolla yesterday. Driver's side was normal, while passenger's side was blue-shifted.

Very interesting, if you can find that picture, I'd love to see it.

Fact is, the automotive headlights are driving the LEDs way harder than it is common with general lighting. Paertially because auto headlights needprecise beam control which needs high intensity packaged to a small area, partly because car headlights use to be designed by far shorter lifetime than general lighting, because simply the cars do not run that many hours over their runtime. Normal passenger car lifetime of 300000km/200000mi means about 5k hours running, headlights are on for barely 1/3 of that, so lifetime of 2k hours means the headlight will last the whole car life, which means less than 1/10 of typical lifetime requirement vs general lighting. And the headlights are really engineered to last just that, to get the required performance at the lowest cost possible, so some degradation effects may already show up, mainly when they do not constitute headlight failure.

And the hard drive may mean different degradation effects than usual for general lighting become dominant. And then there is many years of off state parking time, when the humidity may corrode things without being drawn out by the heat of normal operation.

@Medved -- Good to know! Seems logical that they are engineered to last no longer than the lifetime of the car. I simply find it bizarre that OEMs are sourcing lower-quality assemblies which fail in these bizarre ways... on newer vehicles nonetheless. I think that Corolla I mentioned is still under warranty, so I assume it would be replaced if brought to a Toyota dealer... I find it interesting that it's also an anomalous process, and only few cars are actually plagued with the issue, and not even both lights... this variation and seeming "randomness" is what I find most intriguing. So bizarre to me that they do not fail in pairs as one would expect.

The problem with the "engineering on the edge" is, there is practically no room for any design error, no room for any effect that has been incorrectly neglected. And it is by far not only about normal phzsical or chemical effects, but also about what the real manufacturing is doing on the production floor vs what was assumed during the design.

Why that the LEDs inside automotive headlights would be driven harder than in general lighting? They should be driven the same.

@Medved — True, I just find it odd that they do not fail in batches / pairs of two, and instead one suffers early failure due to poor factory floor quality control? Seems to be the only explanation... probably made overseas in very high volume, and not every unit is perfect...

because the mechanism involves random spot defects, then it is not all pieces the same, but rather a kind of lottery on which piece will be affected and which not. The design then controls just the odds of it happening...

Why that the LEDs inside automotive headlights would be driven harder than in general lighting? They should be driven the same.

They need as high intensity of the primary light source (the LED die) as possible.
Headlights are precise beam control optical devices, where the beam parameters, as well as light flux are strictly controlled by the regulations. To achieve that, the higher intensity the primary light source, the smaller the headlight could be. If you drive a LED by 2x higher current, the intensity will become nearly 2x higher, quite an impact on the total optics size. The efficacy penalty could easily be more than offset by the increased optical efficiency when the light source gets smaller and the car fuel savings smaller, more compact headlight assemblies. And the lifetime in the 5k hour range is more than the rest of the car (mainly the propulsion), so having it any longer won't bring any benefit.

On the other hand general lighting is more about diffuse light, running long hours, so very sensitive to efficacy (because electricity cost is the major operating cost contributor) and lifetime (replacement costs of the light alone are the second highest operating cost contributor). So the designs are more focused to get maximum life and efficacy.

At the end it is all about the cost. But not the cost of the LED chips themself, that is very small fraction. It is about the cost of the complete headlights to make and, more important, the cost required to incorporate them into the car and to solve all the implications related to that, like weight, aerodynamics, crumple zone design (the big holes in the from for the headlight have severe impact on the front structure) and also visual appeal for car buyers. The smaller the optics, the more flexibility is there to design the car, so the easier and cheaper is to design and produce it to still meet the regulations. So ability to achieve any higher intensity is saving a lot of costs at many places, as long as the headlights lifetime is not the limiting factor.

So car headlight the designs go for the highest intensity attainable for the given lifetime requirement, any longer lifetime has no benefit.
Vs the general lighting designs, which go after maximizing the efficacy and the run lifetime. Fitting into standard formats is just enough, any smaller makes no benefit.

In either case do not confuse the lifetime with premature failure rate (failures before reaching the rated lifetime). The later is a problem for both, so the related probabilities are also a factor steering the designs, but mainly the discipline at the production floor.