As if they weren't quirky enough, for the longest time in the 20th century, French cars had yellow headlights. The reason why ...

From 1937 to 1993, the French government required all cars sold in the country to feature "selective yellow lights" for all forward-facing roadway illumination.

I've witnessed headlights transition from sealed-type units to halogen, HID, and LED, back when car headlights had lenses that don't turn yellow or degrade with age like modern plastic headlights.