Red and orange light passes through the atmosphere and is refracted into the shadow zone. Multiple scattering occurs when a ray of light interacts with a multitude of particles. Multiple scattering destroys colors. Milk Clouds Foam Sugar and salt Dispersion Refraction is a function of wavelength. This is referred to as dispersion.
Red light bends the least, violet the most.
The 'rainbows' thrown by lead crystals are more similar to sundogs then rainbows and are more. Sun dogs are generated when light interacts with hexagonal plate like ice crystals that are approximately 30 microns in size and fall horizontally. The ice crystals disperse the sun's light. Notice on the sun dog that the red light is on the inside, as red light bends the least.