Corona of the Moon, The photo below is an observable example of lightwave diffraction. This cool photo of a corona around the moon, which was the astro pic of the day at nasa(apod), inspired me to do some research on how diffraction works. In short this effect is caused by water droplets in the air. There are a great many water droplets and the lightwaves pass between droplet creating an interference wave. The different colours are caused by the fact that each colors different wavelength diffracts at a different angle and the light from the moon is diffracted by many varying widths between the water particles.
A corona is not to be confused with a halo, which is caused by light refraction.
Disclaimer: This photo was distributed by Nasa's Astro Photo of the Day (APOD) and belongs to the photographer who water marked it.