A FLASH OF GREEN
One of the most spectacular solar-terrestrial events, as well as one of the rarest, is the sudden flash of green light seen just as the Sun rises or sets. The green flash, as it is called, is the result of Earth's atmosphere bending different colors oflight by various amounts, especially near the horizon.
You effectively have red, green, and blue suns that set at very slightly different times. The blue sun should be last, but the air usually blurs it out, leaving our final glimpse of the Sun as a flash of green.
To see the green flash, you will need a well-defined, unobstructed horizon and clear, haze-free conditions. An ocean panorama is ideal, which is why the green flash is most commonly seen from ships and from coastal plains and mountains.
Even when setting, the Sun can damage your eyesight, so only ever look at it for a few brief moments at a time.