Let is snow, let is snow, let it snow!
Heck it is hard to get a neutral-white in a headlight, so it might be damn near impossible to get a warm-white, 3000K CCT.
So for colored lights, what color would you pick? (page 12)
http://www.philipslumileds.com/pdfs/DS65.pdf
Myself, I'd rule out royal, blue, and cyan immediately.
Green, although it has the widest spectral distribution, it just doesn't feel like a good work light color. I'd pick it for the firefighter beacon color: red, red-orange, and amber look like fire!, and royal, blue, and cyan don't work with smoke.
Deep red is good for astronomy-protect the rods!, but down on lumens compared to red-orange, which has been done to death.
I like this yellow, it seems the closest to automotive selective yellow, for now.
http://www.lumaray.com/fog_preview_800.html
but isn't up to modern brightness/efficiency standards.
[Direct] amber is the most temperature sensitive, so the cooler it is the more light you get (page 13), but that one advantage [for winter usage] over red-orange was not enough to overcome the lumen deficiency.
Now the phosphor converted amber has put some 'balls' into the light output.
and the SPD is MUCH wider than traditional amber (page 11) 80nm vs. 20nm.
http://www.philipslumileds.com/pdfs/DS62.pdf
So who will be the first to use the PC amber Rebel, a Zebralight H60 "A" perhaps?