The CLEAR glass lens for the fog light (in the 123 series) are indeed available.
I have ONE OF EACH in my 300d
With 1 yellow lens, I get the advantage in fog AND rain/snow....as well as EXTRA light from the clear lens.
Rarely do I get ZAPPED as if I am running high beams.......HOWEVER, when this does occur, I instantly ZAP BACK with my high beams, and that shuts THEM up...
Running with the EXTRA lamps on is something that I do. Not always, however they do offer a little bit of DISTINCTION to the masses.
I believe that either color lenses are available thru the various aftermarket catalogues etc. aprox $45/$50 each.
Or go the boneyard route and keep one extra on hand for when they crack
Lets keep those diesels humming.