From The Durango Herald (Liz Weber):
But what is it about the setting sun – what science – explains the variation in colors and intensities we see evening to evening?
“At sunset, the atmosphere acts like a color filter, scattering blues and greens out of our view and leaving behind reds, oranges and yellows,” said Joanna Casey, visiting instructor of physics and engineering at Fort Lewis College…
In Southwest Colorado, reflective surfaces along and above the horizon, like the mountain faces and the clouds that surround them, act like projection screens, Casey said. That environment makes for an “extra spectacular sunset venue.”
In the desert, sunsets often have deeper reds and oranges. That’s because the lower horizon means there’s more atmosphere to pull out blues and violets, said Michael Ottinger, dean of the School of Science, Math and Engineering at San Juan College…
Other factors can affect the colors and intensity of a sunset, whether in the mountains or desert.
For example, moisture or pollution particles in the air can block a lot of the sunlight, dulling and diluting the colors, Casey said. Therefore, when the air is very dry, as it often is in the desert, there will be brighter sunsets.
Winter in particular can have spectacular sunsets because freezing weather pulls even more moisture out of the atmosphere, Ottinger said.
Clouds also affect sunset colors. In particular, when light hits low-lying clouds, sunsets may produce brighter oranges and yellows, Ottinger said.