Ever wondered why fog lights come in different colors? You’d be wrong if you thought white and yellow lights were just a defining style. The color of your fog lights is there for a reason: they play an essential role in how much light can penetrate through the fog to help you see. What is that role, though?

Visibility: How is that measured?

White and yellow light operate based on what is known as the Visibility Index (VI). It suggests a number representing how well drivers can see with the naked eye. This visibility scale ranges from 1 to 10, with 1 being extremely low visibility conditions such as heavy storms and 10 being clear, sunny skies with unlimited visibility.

The color of your fog lights affects their performance in different situations depending on your car VI falls on the spectrum.

As such, what should you take into account?

Glare

Glare can be a problem when driving at night. Glare is caused by light reflecting off a shiny surface, such as a patch of wet road or a clean, shiny car body. This light bounces back into your eyes, reducing the visibility on the road ahead.

The white fog light produces more glare when compared to the yellow fog. This is because white light is more concentrated, has less color, and therefore does not scatter as much as yellows do.

The Bright Side

Yellow may be the color of sunshine and happiness, while white makes you squint, like the glare off freshly fallen snow. Although yellow is nice, but it doesn’t wake you up like a cup of black coffee (or infinite numbness).

The same goes with fog lights. A critical difference between the yellow and white light is brightness.

Once upon a time, yellow fog lights used to be the norm since the yellow filters the light to reduce glare, making it easier for other drivers on the road. However, as lighting technology progressed, bright white light was invented since it is brighter and more effective at illuminating your path.

Color Temperature

Let’s start by clearing up the dilemma between color temperature and brightness.

There is a common misconception that the higher the Kelvin reading on a light bulb, the “whiter” it will appear. More specifically, white lights may appear brighter than yellow ones, but that’s because the human eye is more sensitive to them.

That is not true. The Kelvin scale measures color temperature, which only has to do with perception and not actual brightness. Hence, changing the color temperature does not change actual brightness and can result in a spotty or uneven light if all bulbs are at different temperatures.

Additionally, white fog lights tend to have higher brightness, ranging from 5000 to 6000 kelvins. On the other hand, yellow fog lights vary from 2000 to 3000 kelvins.

It is generally true that white lights may appear brighter than yellow

Considering this, you might be thinking: “Hm, since 10,000K is brighter than 6,000K, maybe I should just get the 10,000K bulbs and call it a day.”

Well, not so fast! There’s more to this story than meets the eye. Before jumping to any conclusions about which bulb to buy for your vehicle’s fog lights—or any lights for that matter—it’s essential that we understand how different colors of light behave in different situations.

So, how do we perceive colors?

When we look at something, the light enters our eyes and is processed by our brain. We see the color of an object because it reflects specific wavelengths of light to us, and other wavelengths are absorbed. For example, green objects reflect the wavelength that appears green to us while absorbing all others. Your brain then translates these reflections into the color green.

However, when you’re looking through thick fog or smoke, the situation gets more complicated than when you’re looking at something that merely blocks out the incoming sunlight and casts a shadow on your retina. 

More specifically, the human eye is sensitive to a particular wavelength or colors, with yellow at 589nm and white at 695nm. When there is fog or poor visibility, the light reflected from water droplets makes it challenging to see clearly.

On this account, instead of absorbing some colors and reflecting others, most objects are transparent to some degree in this scenario. In other words, they let some light pass through them unaltered while still blocking other frequencies of light waves from entering your eye. The result is that there’s not just one color being reflected into your eyeball; there are many.

The Science of Fog Lights’ Color

At this point, you might be thinking that the right answer is clear as day: fog lights must be white. (This is a pun. Please laugh.) But despite the innate logic of this conclusion, it appears that science has other ideas. 

  • Light intensity

More light means that you’ll be able to see farther and better. For example, this is why streetlights usually look a bit too bright when they’re turned on in the middle of the day—there’s enough ambient light that extra brightness will just scatter off clouds or mist and do very little good.

The wavelength of the light

Different wavelengths behave differently as they come into contact with water droplets suspended in fog or mist—and some are much better at getting through than others! This one is a bit harder to wrap your head around, but as an analogy: imagine throwing rocks at a window made of clear glass and one made of frosted glass (the kind used for shower doors). 

If you throw rocks that are big relative to the size of the holes between sheets of glass (e.g., huge rocks), then both windows will be equally easy to break; but if your stones are small relative to those holes (i.e., really tiny stones), then it will be much easier for them to slip through the regular clear window than it would be for them to get past frosted glass without bouncing off first.

Foggy Eyes, Foggy Sight

Let’s talk about how yellow and white fog lights affect the human eye because, without understanding that, it’s hard to decide on which color to choose.

Colors and Fog Lights

A similar process applies in the case of headlights and fog lights – they produce a certain wavelength to be seen by our eyes and brains. Sometimes, this can be tricky: when you’re driving through street lights or fog lights at night, your pupils get smaller to keep out all the extra light being produced by surrounding lights. This is why sudden bursts of bright headlights seem overwhelming, even though we can typically see them just fine when driving in normal lighting conditions.

Since yellow light lies towards the center of the visible spectrum, yellow fog lights make it easier for the human eye to perceive them more accurately and thus improve the visibility even during low visibility conditions such as rain, snow, or fog. On the other hand, white light has a longer wavelength, making it harder for us to process that information accurately in our brain when there’s very little visibility.

What About Amber Fog Lights?

The difference between yellow and amber fog lights is a matter of optics. It’s difficult to see the difference with the naked eye, but with scientific instruments, you can notice that yellow light has longer wavelengths than amber light. 

In practice, amber beams combine red and yellow, creating a warm glow that isn’t too harsh on the eyes. Yellow headlights use purer yellow or may have a combination of yellow and green, which gives off a brighter glow than amber fog lights. Fog lights are typically in the high-intensity discharge (HID) family of light sources, with more lumens per watt than incandescent bulbs.

In addition, the yellow-green shade tends to be more common in fog lights because this color typically provides a neutral color with a good view.

Car manufacturers have agreed that this naming convention makes sense, so they label their products according to what colors are used in each product’s manufacture.

Yellow (Amber) Fog Lights vs. White Fog Lights

Wavelengths 

Yellow light has a shorter wavelength, which is less intense than white light. It’s also more visible due to the shorter wavelength. 

White light, on the other hand, has a longer wavelength and is more intense than yellow light. This makes it easier to reflect and causes glare.

Therefore, yellow lights could be considered preferable for low visibility conditions and white ones for higher visibility conditions. As such, for standard driving conditions (i.e., moderate visibility), white lights may be a better option.

Reflection

The strong scattering effect of fog particles causes the fog to refract light towards you. It’s as if you’re in a cloud of tiny mirrors all around you, reflecting everything at your eyes, making it difficult for you to see anything ahead of you clearly. 

In this case, yellow lights are less likely to get reflected off those mirrors (fog particles), which then helps you see through the fog better without getting blinded by the reflected headlight beams from the vehicle ahead of you or even your own vehicle’s headlamps reflecting off those mirrors (fog particles).

Visibility

Consequently, when it comes to penetrating thick fog where visibility is low, yellow lights may be better than white ones because they produce a more dispersed beam of light–which is excellent for getting all over a large area quickly and efficiently, like when visibility is low. 

However, when it comes to areas with higher visibility, like thinner fog or night driving conditions with no fog at all, white lights outperformed yellow ones because they produce a more concentrated beam of light that was capable of greater penetration through the environment–which is ideal for seeing further down the road and into blind spots!

Daytime vs. Nighttime

White light is ideal for nighttime driving. It offers the best visibility and helps you see everything ahead of your car, including animals, oncoming traffic, and other potential hazards on the road. However, yellow light has better contrast in low-light conditions such as rain or fog, so it can help you see better during those conditions (even though this isn’t its actual purpose).

To Clear Things Up

The answer to all precautious drivers’ questions: it depends. Both yellow and white light have their pros and cons, depending on the intended purpose.

  • Suppose you’re looking for fog lights strictly designed to combat heavy fog and maximize your vision during low-visibility conditions. In that case, yellow lights may be your best bet: they’ll spread across a smaller area faster than other headlights would allow. 
  • Yellow light reduces the glare to other drivers. Because of the selective yellow light, it reduces the glare to other drivers. It is more effective during fog as well. You also have to be careful using your high beams when it’s foggy or snowy outside because you can cause visibility problems for other drivers. White light is more confusing and unfocused in foggy conditions.
  • Yellow light is harder to see during the day. The human eye is more sensitive to blue rather than yellow light, so it takes a bit of time for the eye to adjust quickly to such light. If you’re driving in an area with high humidity, yellow fog lights might not be as helpful as white ones because they will reflect off the moisture in the air and make it even harder for you to see through the fog.
  • When it comes to higher visibility, the best options would be white fog lights since they offer a higher degree of penetration through the inclement conditions, an ideal aspect for seeing further down the road and into blind spots.
  • White light is preferable in heavy rain and snowstorms. It will illuminate the road better, while yellow light has a harder time cutting through these inclement conditions.
  • White illuminates the road better, since yellow glass essentially filters the visual spectrum of the light. It creates a darker environment by filtering out more light than the human eye can perceive.

Regardless of the color of your fog lights, keep in mind that these auxiliary lights and just half the story. Having good lighting will only be helpful if you’re driving safely while using them as well. Before turning on your bright lights, closely monitor all vehicles around you and wait until they are far enough away from you before activating your bright lights so that your car’s brightness blinds no one.