Answer to Question 1
Answer: The larger solar angle at sunrise and sunset allows for less refraction at longer wavelength colors (such as red and orange) than for the shorter wavelength colors (such as blue and green).
Answer to Question 2
Answer: In addition to slightly shifting the apparent position of the Sun near the horizon, refraction can also affect its apparent shape and color. Sometimes, near dawn or sunset the Sun seems to have horizontal bands of different colors, with redder coloration near the bottom. This occurs because longer wavelength colors (such as reds and oranges) undergo less refraction than do shorter wavelength colors (such as blue and green), as described above. The shorter wavelengths, undergoing a greater amount of refraction, concentrate near the top of the apparent sun, while the longer wavelengths locate near the bottom. Under some atmospheric conditions the Sun appears momentarily to be capped by a bright green spot, known as the green flash.
