Yup, and they are an American thing.
It's one of the things that need to be changed when you import a car to Europe (well, some parts of Europe at least).
You know what's worse?
No car built after 1970 may have red turn signals at the rear in Germany.
You must convert to yellow. Well good luck doing that on most American cars.
Here in Luxembourg they are also not legal but "accepted". They still "warn" you at each inspection though, mentioning them in the papers as not conform to rules but not enough to reject the car. Classic "gray area".
Staying in Luxembourg: no yellow sport lamps and no yellow position lights up front and no side markers are allowed.
If you look closely at my car you'll notice that I have fabricated my own white lenses for the lower valance.
Yellow is only allowed for turn signals and no yellow light can stay on permanently except for fog lights which in turn must comply to a whole another set of rules.
This is also why I always remove the sport lamps for inspection and replace them with my own custom made "sport lamp delete plates".
Oh, the joys of bureaucracy.