A typical reason is that most devices (such as solar cells) for converting the incoming energy to useful output are relatively small and costly, and they work best at converting directional light at high intensities and limited ranges of frequencies, whereas input radiation tends to be diffuse and of relatively low irradiance and saturation.
This use of immediate—sometimes incongruous—contrasts has an exaggerative effect on the foreground’s strong colour saturation; itself a component in the effect of aerial perspective.
Though color management software, such as that built into image editing applications, will pick the closest in-gamut approximation, changing lightness, chroma, and sometimes hue in the process, author Dan Margulis claims that this access to imaginary colors is useful, going between several steps in the manipulation of a picture.