Physiology
The effect occurs because the color-sensitive cones in the retina are most sensitive to yellow light, whereas the rods, which are more light-sensitive (and thus more important in low light) but which do not distinguish colors, respond best to green-blue light. This is why humans become virtually color-blind under low levels of illumination, for instance moonlight.
The Purkinje effect occurs at the transition between primary use of the photopic (cone-based) and scotopic (rod-based) systems, that is, in the mesopic state: as intensity dims, the rods take over, and before color disappears completely, it shifts towards the rods' top sensitivity.
Read more about this topic: Purkinje Effect
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