Natural Phenomenon: Nacreous Clouds

Polar stratospheric clouds (PSCs), also known as nacreous clouds (from nacre, or mother of pearl, due to its iridescence), are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 m (49,000–82,000 ft). They are usually spotted only near the poles, nacreous clouds form very high in the atmosphere (twice as high as commercial airplanes fly), where the air is particularly cold and dry. However, they are best observed during civil twilight, when the Sun is between 1 and 6 degrees below the horizon, as well as in winter and in more northerly latitudes. 

The colorful shine actually comes from the setting sun being lower in the sky than the clouds, so they reflect sunbeams back toward Earth.

Unfortunately, while they're beautiful, nacreous clouds also destroy ozone, the compound that protects us from the sun's most dangerous rays. They are implicated in the formation of ozone holes. The effects on ozone depletion arise because they support chemical reactions that produce active chlorine which catalyzes ozone destruction, and also because they remove gaseous nitric acid, perturbing nitrogen and chlorine cycles in a way which increases ozone depletion.

Source: Wikipedia and businessinsider.com