While out and about in the yard today I spotted this. Ice, with a layer of air beneath it, exhibiting colors. The colors are only apparent when viewed through a polarizer, such as the sunglasses I was wearing. And that I put in front of the lens of my iPhone to take this shot.
By the time I was able to get inside the house, grab my DSLR, put the polarizing filter on the lens, and get back outside the original ice had melted. But as you can see above, there was more ice. And the sun was just hitting it. And the colors were quite nice.
And they varied with the angle between the lens and the ice. Above we see the dominant hue is yellow.
Now it is purple.
And finally green. Very cool (physics is fun!).
The key to the colors, as can be learned a the wonderful Atmospheric Optics site, is the layer of air beneath the ice. As it is the reflection of the light at the ice-air interface that leads to the colors, via the phenomena of "birefringence".
... and Above
When I looked up instead of down I saw a 22ยบ halo around the sun. Formed by the ice crystals that make up the clouds.
And here we have an image of both halo above and the ice (bottom edge, center) below.
The moral of the story is to keep one eye looking up and one eye looking down. Or just look around a lot. That's what I do.
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