Low-level clouds can show intense colors during sunrise or sunset. The coloring occurs right after sunset (or before sunrise), as the clouds are close to the ground. Higher clouds will catch the sunlight for a longer time, and will be reddish or orange for a much longer time. But since low clouds are usually close to you, any reddening can be spectacular, since haziness won't have much of an effect on making the colors dull as it would do for higher clouds.
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