Photo Credit: Albert de Nijs
Nacreous, or Mother of Pearl Clouds are comprised of tiny ice crystals and form in the stratosphere. They are mostly found in the polar regions as a temperature around -85 °C is needed for them form. During the day, they look like high cirrus or lenticular clouds, and only become colorful after the sun has set. Once the sun dips a few degrees below the horizon, the ice crystals reflect the light, giving the clouds an iridescent appearance. Once the angle of the sun increases, the clouds become more uniformly colored.
I would not never expect to see clouds like this. It looks like someone painted them into the sky. This image and clouds truly show the beauty of nature.