I was expecting a typically gorgeous Colorado sunset on this day not long ago but it was the pre-show about a half hour before that was the best part. Iridescent clouds appeared and turned the sky into a rainbow of colors. It was an awesome one seen from my backyard.
Cloud iridescence is caused by clouds (usually cirrus) that have small water droplets or ice crystals in them causing the light to be diffracted, or spread out. The phenomena is much like the rainbow colors seen with oil in water.
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