I'm thinking of installing a pair of Hella 500 fog lights. Which would give the best lighting pattern/brightness, fog lights with amber lenses or clear?
Also, is there any advantage to using fog lights with clear lenses and installing amber bulbs?

Thanks in advance for your thoughts and experience on this subject.

Ken C., thanks for a very informative run down on my lighting issue. It helped alot. I'll stick with the clear fog light unit for my application. I hope it answered any lighting questions anyone else may have had in the back of their mind.......

First, let me ask you to not become one of those "bimmer drivers" who has to keep their fog lights on all the time and, to add insult to injury, has them turned upward so they blind everyone else ("Gee, I'm only using my low beam headlights"). Fog lights are supposed to be aimed so that the upper cutoff slopes downward, diminishing in height with distance.

That said, while yellow fog lights "look good", you can turn to an objective, empirical source for advice. Bosch, in their reknowned and trusted company publication, "Automotive Handbook" (a publication that tells you almost everything about the engineering of virtually all systems in automobiles) states that the popular notions of the benefits of using Yellow foglights are untrue:
1) Any foglight with a yellow lens reduces its light output below its bulb's potential because the yellow tinting is a filter, and absorbs otherwise useful light.
2) Yellow light does NOT reduce backscatter (reflection of light from the lamps, off water droplets and/or snow, and back to the driver's eyes) -- the reduction in perceived glare is an illusion, only due to the reduction in intensity of the light. The wavelength of yellow light is NOT more conducive to penetrating (rather than being reflected by) water droplets.
[As a professor of human physiology with a biophysics background, I can add that this idea may have come, historically, from the effective use of "yellow" lens to sharpen vision -- e.g., shooter's glasses -- but that works by a different principle, that of reducing the human eye's chromatic abberration (i.e., different colors focus on the retina at different points, reducing the sharpness of an image), and therefore by diminishing the various colors seen other than one (yellow) this eliminates those other points, something that the human retina does anyway viz. it's macula lutea, a yellow-pigmented tissue over the fovia. This is why using yellow lenses enhances sharp vision -- the yellow lens is an adjunct of the natural macula lutea -- it's more of the same color. But this is not the same as using yellow for fog lights -- you are trying to reduce backscatter to more effectively penetrate fog or snow and see objects farther ahead, rather than focus (and therefore see) objects more sharply.]
3) The use of yellow fog lights, as in using any monochromatic (one-color) light, risks a failure to adequately illuminate an object that is not that color! That is, while yellow objects (which reflect yellow light) will be illuminated, objects of other colors (red, blue, etc.) absorb all colors other than their own, and therefore will absorb the yellow foglight's light rather than reflect it back to the drivers eyes.
[That is, non-yellow objects are actually darkened (and harder to see) when illuminated by yellow light -- this is simple Physics 101.]
4) The best choice is a white light that is "well-designed".

In a conventional fog light, a "well designed" foglight is one that has:
a) a rear reflector that efficiently collects and redirects all the light from the filament forward;
b) a front front lens that focuses the light properly into a useful beam;
c) a light shield that creates a sharp, top-edged cutoff (don't buy a lamp without this internal metal cutoff -- as no lens alone can accomplish this effectively).
d) good seals, to prevent corrosion of the reflector.
And in newer designs, such as PES (polyellipsoid) and projector lamps, also look for comparable quality.

By the way, HID foglamps (there are a few makers, such as Hella) are superior in their "efficiency" (light output or lumens per watt), but not all brands are necessarily high-ranking in their beam's quality (directing the beam, and controlling cutoff); they may only compensate for poor focusing of the light by the brute force solution of just generating more light, but the poor spillover will just annoy (or worse) other drivers and create more glare for you to endure. Again, think quality!

Good luck. And please, properly aim your fog lights, and just use fog lights for fog and snow.

Thanks.

Hi, again. In rereading the next day what I wrote, I forgot to add, for anyone installing and aiming their fog lights, that:

1) aiming fog lights downward enhances its benefit to the driver (in addition to being considerate of others drivers ahead). Noting that the ideal goal of foglights is to illuminate the road and obstacles ahead while minimizing backscatter and glare, by aiming down, you are placing the beam below your line of vision -- and therefore minimizing the light that will reflect back in your own eyes. Mostly only objects and obstacles that appear in the beam, because of their surface, will reflect light back at you. Thus, lower aimed fog lights have more penetrating ability and less blinding glare.

2) Remember, foglights are NOT driving lights -- their design (e.g., their top cutoff) is for bad weather, to help you see in conditions of rain and fog and snow.
Admittedly, some folks use fog lights as an adjunct to their low beams in the country, to see as they go around a country road's curve, because of the fog light's wider beam pattern. That's OK, as long as the lamps are aimed low. Better is to replace your headlights with European E-code headlights, whose beam pattern will provide the wider coverage you seek, and also has a sharp cutoff similar to fog lights.

3) In contrast to fog lights, Driving lights* are meant for clear nights (not bad weather, when they'll just cause glare back at you and reduce your own visibility). They are not fog lights, and shouldn't be used in traffic, but are an adjunct to, and should be "on" only when you can also use, your high beams. Turn off driving lights (and also don't use high beams) in bad weather, as their light will readily reflect back in your eyes and reduce your vision of the road ahead.
[ * There are other lights ("auxiliary lights" I recall) that are supposed to be used as an adjunct to low beams, but they have a special beam pattern that is similar to fog lights but with a central "hot" spot -- these can be used with low beams in traffic without blinding other drivers; but these are not "driving lights" and they shouldn't be confused with them.]

Good luck, and be considerate of other drivers' vision. We're all trying to see at night, not just you!
Thanks.