Reply #5: Try experimenting with shooting for a while after the color seems to have faded.

[ConsAreLiars]

The human eye has both color sensor (cones) and B/W brightness sensors (rods). The result is that as the light fades, the colors may change but not be gone. Too dimly lit for the cones on the retina to respond and react to, so we see only grays, but with a long exposure the camera sensors will pick up the color.

(edit typo)