The human eye can detect shape, size, distance and movement, as well as colour in order to collect information about your surroundings. Colour is one form of sensory input that your brain uses to interpret important elements of your surroundings.
Rods and Cones
Rods are the cells in the eye that are sensitive in low light conditions and do not perceive colour. Cone cells, however, function in bright light and are colour sensitive. When light rays strike cone cells, a chemical reaction occurs in the cell that causes an electrical impulse to be sent to the brain. The greater the input, the greater the signal to the brain.
Nervous System Input
The nervous system requires sensory input, so much so that lack of sensory input, such as solitary confinement, is a form of punishment. Colour addresses one of the basic neurological needs for stimulation, according to Color Matters.
Colours that have a metallic component or shine are especially attractive to the eye. As people move from place to place, they have a deep human instinct to look for water. Very bright, glittering light is a signal that water may be near.