Why is it only red? Because there was only a red color. All the other colors of the rainbow were scattered by air molecules and dust particles in front of the low-hanging sun. The sunset rainbows are often red, since the intensity of scattering and refraction for different wavelengths is not the same. At sunset, the rays of the sun go a long way in the atmosphere and longwave light (red) dissipates less than the shortwave. As a rule, red rainbows still form a full arc, but this did not work out – because of the clouds. Shadows of clouds near the setting sun stretched across the sky, muffling most of the rainbow. There is only one almost horizontal strip.
