If I use amber light as headlight during daytime, rainy/foggy days, is there the risk of being mistaken as a taillight by drivers and thus causing potential accident?

Probably not if you also have a normal headlight.

Then of course not problem, but I meant if I use only amber light for daytime (I use normal white light at night).

In some states it might be illegal, I think in NY you're only allowed to have forward facing red/orange if you're an emergency vehicle.

For daytime fog use, I think that would be a great idea. I use my headlight in blink mode for those conditions. Either way will make you more visible than just a white light in fog.

Amber headlights have never been common in the US. Therefore, drivers will not immediately recognize them as a "headlight." They may have to think about it for a second. Unfortunately they may be mulling it over while moving toward you at 70 feet per second.

Also, colored lenses absorb some light, so amber headlights are less bright than white headlights. And they "look" less bright too.

The most important function of a bike headlight on the road is to get drivers' attention and communicate "I'm a vehicle". To get their attention, the light should be bright and ideally flashing. To communicate, the light should look like a headlight, not some puzzling yellow thing.

The yellow lens is a filter, so it reduces the amount of light, ..same with colored reflective tape.

Thanks. Seems most of you think it's not a good idea. What about using it as taillight in daytime (instead of red taillight)? Some people say amber is more noticeable than red (some say even more noticeable than white).

I think most people are expecting red on the rear of a vehicle and white or yellow on the front because thats the legal convention AFAIK. I'm running ambers in front myself but also have white that can be kicked in if circumstances require. Amber (or any other color) LEDs are currently less powerful than the most powerful white LEDs but 300 lumens x 2 can still make you very conspicuous.

Contrary to some opinions stated here - hazard lights are standard on automobiles and easily recognized. The actual choice of equipment counts. Guarantee that my amber lights are brighter than the dinky white things some people are using. Visibility counts FIRST. But check your area - in some places a bike is required to have a white front light after dark.

Did someone give you an amber light you're trying to find a use for? No reason to not have multiple tail lights, just attach it to your backpack/panniers/jersey pocket/seatpost and go nuts.

Food for thought: If amber is considered such a poor choice (for the exact scenarios the OP describes), then why would a reputable company like Dinotte offer one?

IMO, amber is a legit choice for the scenario described by the OP. Why? Because the hazard lights of slow moving vehicles are amber (or they used to be, I haven't kept up with automotive lighting tech for a while now).

I don't see a problem with confusing anyone. Flashing amber lights are commonly used in a variety of ways to warn of things that should be avoided - construction sites, dangerous curves, bad potholes/bumps, slow-moving vehicles, etc. So I see no reason why a driver would think of steering toward rather than away from such a light even if he doesn't immediately recognize it as a bicycle. Seems like an excellent choice for daytime use on a bicycle since it is likely to stand out from other lights and reflections much better than a white light.

Anecdotal input.. I saw a guy with an amber headlight yesterday while riding, he was coming from the opposite direction it was daylight and it was off putting but I was never confused as to his direction of travel.