photochromic Lenses have been around for decades. I use photochromic goggles every time I dirt bike, no batteries or solar panel.
For faster response on the street I use a shoei helmet with drop down tinted lenses inside. Just a flick of the finger slides them down over my eyes. Simple, cheap, effective. Pretty sure it’s SNELL approved.
I don’t want complicated and expensive. $460 buys a few tires.
Polished silver hides scratches. For that reason alone I’d take silver over black most times. Of course there are applications where black just looks great (carbon fiber). But rub marks on $300 cranks never look good.