Averted vision works because there are virtually no rods (cells which detect dim light in black and white) in the fovea: a small area in the center of the eye. The fovea contains primarily cone cells, which serve as bright light and color detectors and are not as useful during the night.
Averted vision operates because the fovea lacks virtually all rods, specialized cells for detecting dim light in shades of gray. Instead, the fovea contains a high concentration of cone cells, which excel at processing bright light and colors but are less useful when visibility is low.