Explanation:
Why would a cloud appear to be different colors?
A relatively rare phenomenon known as
iridescent clouds can show unusual colors vividly or a whole
spectrum of colors simultaneously.
These
clouds
are formed of small
water
droplets of nearly uniform size.
When the Sun is in the
right position and mostly hidden by thick clouds,
these
thinner clouds significantly
diffract
sunlight in a nearly coherent manner,
with different colors being deflected by different amounts.
Therefore,
different colors
will come to the observer from slightly different directions.
Many clouds start with uniform regions that could show
iridescence but
quickly become too thick, too mixed,
or too far from the Sun to exhibit striking colors.
This iridescent cloud was photographed above
Boulder,
Colorado last week.
