and gives brighter lenses than the Chrysler ones which were very difficult to see, even with LED bulbs behind the glass.
That makes perfect sense, thanks for the detail! LED certainly exaggerated the problem, but even a conventional bulb was very dim behind the old lenses, they are incredibly thick and not particularly translucent. I'm not sure if standards were much lower in the 20s for illumination or if they had become more opaque over time.I tried this in an old Volvo of mine. A bit of armchair science (and do correct me if I'm wrong):
You create red light by placing a red piece of glass in front of a bulb. The bulb puts out a broad spectrum of colours and the red glass filters out all the wavelengths that aren't red.
A LED bulb doesn't have a very broad spectrum. That's how it manages to be brighter while using less power - you're cutting out most wavelengths including the invisible ones - and most of the red. So when you put a red filter in front of a bulb that doesn't put out much red, you're left with nothing.