Interesting. I've been skeptical of the blue or purple lights. Whenever I've been in a car that had those, I've always thought the visibility was bad. My thought is that our eyes have evolved to be most useful in sunlight, which is whiter, and slightly blue so anything other than that would make it more difficult to see. Filters dimming the light does help to explain reduced visibility.
There is a YouTube channel called Headlight Revolution where they did a comparison of 12 different LED headlights, measuring the lumen output, observing beam pattern and testing them on a dark road. That helped me decide on the ones I bought. This particular series is focused on purpose built LED headlights, headlights designed from the ground up for LED use, rather than something like an H4 conversion bulb. They do review other types of lights on the channel, as well.
https://www.youtube.com/watch?v=1qStRHOFRcY&list=PLhombf0sgTNy-fsw4tf24UzBKHGQEoX7D
Lawrenceville, GA