It is usually at some level systematic or coherent , but never accidental.
Art is designed .
The function of the color is to enhance contrast while decreasing the strain on the eyes one would experience from a darker color. Even so, it suggests something alive, while quietly admitting a harder, metallic nature. This ultimately has the psychological effect of bridging the animate, inanimate, and concrete in an abstract manner. Like life itself, it carries with it the dust of prior experience, otherwise wiped out. We are not seeing the object through our eyes, but through the mind of the artist.