At long distances, I am more accurate at night when my peripheral vision sees a flash of a dark someone move against a lighter background: in such cases, something in my optic system and brain quickly tosses up the person's gender at the same time it alerts me that someone is there at all. Once I focus on them and look directly at them, I have difficulty telling until they have moved enough in the light for me to be able to do better curvature and facial recognition, and eventually I can say, "Ah yes, it is a ____ after all!". There are roughly 20 times as many rods (not color sensitive) as cones (color sensitive), and rods are much much more sensitive, so it does make sense that one might perceive something in black and white that is more difficult to see in color (focusing on it.)
