Clouds can take on virtually any color, but are usually white or shades of gray, depending on the weather. Nacreous clouds, on the other hand — also known as mother-of-pearl clouds — can take on brilliant, iridescent hues and look like watercolor paintings in the sky.
By day, nacreous clouds often resemble pale cirrus clouds. But after sunset, magic happens as the colors come out.
These hues are most vibrant when the sun is several degrees below the horizon. Then, when the sun sinks below the horizon, “the colors are replaced by a general coloration that changes from orange to pink and contrasts vividly with the darkening sky,” the International Cloud Atlas notes.
These clouds most commonly appear in the Arctic, Scotland, Scandinavia, Alaska, Canada, the northern Russian Federation and, as pictured here, in Iceland.