While 'Googling' something over the weekend, I saw a reference to the phenomena of the "Green Flash" optical illusion that can sometimes be seen at sunset or sunrise. I had never heard of it before, so more 'Googling' led to this description by LiveScience:

"A green flash, which occurs more commonly at sunset — but can also occur at sunrise — is a phenomenon in which part of the sun can be observed suddenly and briefly changing color. It usually lasts only a second or two — which is why it is referred a flash — as the sun changes from red or orange at sunset, for example.

The green flash is viewable because refraction bends the light of the sun. The atmosphere acts as a weak prism, which separates light into various colors. When the sun's disk is fully visible above the horizon, the different colors of light rays overlap to an extent where each individual color can't be seen by the naked eye."

We'll have to check with our photographer friend Mike Skywatcher to see if he's captured this beast yet on film.