Cloud iridescence - AbsoluteAstronomy.com

Cloud iridescence is the occurrence of colors in a cloud

Cloud

A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...

similar to those seen in oil films on puddles, and is similar to irisation

Irisation

In meteorology, irisation, a type of photometeor, is multiple mixed iridescent colors caused by sunlight being diffracted in clouds. The colors are often brilliant and mingled together, sometimes similar to mother-of-pearl. They sometimes appear as bands parallel to the edge of the clouds...

. It is a fairly uncommon phenomenon, most often observed in altocumulus

Altocumulus cloud

Altocumulus is a cloud belonging to a class characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. Like other cumulus clouds, altocumulus signifies convection...

, cirrocumulus

Cirrocumulus cloud

Cirrocumulus clouds are one of the three main types of high-altitude clouds, which also includes cirrus clouds and cirrostratus clouds. They usually occur at an altitude of to . Like other cumulus clouds, cirrocumulus clouds signify convection. Unlike other cirrus clouds, cirrocumulus include a...

and lenticular cloud

Lenticular cloud

Lenticular clouds are stationary lens-shaped clouds that form at high altitudes, normally aligned perpendicular to the wind direction. Lenticular clouds can be separated into altocumulus standing lenticularis , stratocumulus standing lenticular , and cirrocumulus standing lenticular...

s, and very rarely in Cirrus cloud

Cirrus cloud

Cirrus clouds are atmospheric clouds generally characterized by thin, wispy strands, giving them their name from the Latin word cirrus meaning a ringlet or curling lock of hair...

s. The colors are usually pastel, but can be very vivid. Iridescence is generally produced near the sun, with the sun's glare masking it, so it is more easily seen by hiding the sun behind a tree or building.