Explanation: Why does a cloudy moon sometimes appear colorful? The effect , called a lunar corona , is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colors has different wavelengths , each color diffracts differently. Lunar coronae are one of the few quantum mechanical color effects that can be easily seen with the unaided eye . Solar corona e are also sometimes evident. The featured image was taken last month from Paris , France . The blue beacon emanating from the Eiffel Tower did not affect the colorful lunar corona .