I want you to look really close at the picture above. I snapped this last year on Memorial Day, then forgot to post it. It's the sun setting, just moments before it sinks below the horizon. It's that little spot just to the left of center. It should be orange, but if you look closely, it's not. Here, let me blow it up for you.
Here's a way-zoomed in view of the picture above, way bigger than I should blow it up, but I want you to see what's there. The sunset has actually turned green. It's called a green flash, and it's a rare by-product of some interesting atmospheric phenomena. Some people claim to see it all the time, some folks claim it doesn't exist, but here's the photographic proof that I shot with my own camera. Note how the image of the sun seems to hover above the waters' surface, not actually touching it. That has something to do with a temperature inversion near the surface of the water. It's causing an optical illusion, channeling the light in odd ways, and scattering all the yellow, orange and red light, leaving only the green.
This is a detail from the next frame I shot, showing it's still green, only there's less of it.
The frame after that, still green, but nearly gone. There was nothing at all in the following frame. These photos all show a timestamp within one second of each other, and my camera can take about 8 frames per second, so I suspect this series of pictures runs less than a second. I don't recall if I had it on high-speed capture or regular. I usually leave it on regular because it gets touchy on high-speed and I end up with a dozen picture of the same thing.
And this is the frame that precedes all of them, before the sun reached that critical spot where all but the green colored light is scattered into the atmosphere and lost. If I were just throwing a green filter on it, then this shot would be green, too. For the technical minded, I shot these handheld with a 7D and a 400mm lens (626mm it says, with the EF-S sensor). Whenever I've been at the beach hoping to catch a green flash with tripod and all, it never happens...