My lovely and talented wife has a habit of being in the right place at the right time to capture nature doing interesting things. This particular shot was taken by cell phone from a moving vehicle in Northern California last night and shows something I’ve never seen before.
Those of you looking for the elusive “green flash” at sunset might never have considered that you can also get the full spectrum of colors too.
This is looking into the sunset, and isn’t your typical rainbow where the sun is illuminating from behind at sunset, such as this one from NASA APOD.
Note: depending on your computer monitor and its settings, you may or may not be able to make out the spectrum. Some adjustment might be needed. What works best for Internet browsing isn’t the best for photos.
Ice crystals in the atmosphere is what I think is the most likely explanation, making a circumhorizontal arc, which is an optical phenomenon. Basically it is an ice-halo formed by plate-shaped ice crystals in high level cirrus clouds. In the photo above, only part of the arc is visible.
An example:

Jules Verne wrote a story about the green flash called “The Green Ray”. A couple was standing on a hill waiting for it, but just at the crucial moment their eyes meet and… they miss it! But they realize they are in love, so it all ends happily.