At first, the dark band in between seems so counterintuitive, but then your realise rainbows don’t create extra light, so it has to come from somewhere. Alexander’s Dark Band is the empty husk left behind after a rainbow is born.
So I don’t know if I got a picture, but I was at a local beach right at sunset, and we had this moment where, for like just a moment, the entire valley behind us lit up with rainbows. Not a double rainbow, but like 5+ deep ‘double’ rainbows. It was utterly surreal.
That doesn’t explain the gay frogs, at all.
AAAAAAA DOUBLE RAINBOW
All the way!
So how do triple rainbows work?
Light bounces around and exits a raindrop in many different directions. This graphic illustrates the first(brightest) two that hit your eye, but there will be a third, fourth, etc in decreasing brightness.