Here's the gist of the secondary blind spot, which occurs in low light situations:'
"Unfortunately there are a number of drawbacks using only night vision.
Among these are:
The inability to distinguish colors. No detail can be seen (about the same as 20/200 vision in daylight). That nothing can be seen directly in front of the eyes (no rods in the center of the retina), you must learn to look about 15-20° off center.
Only motion can be detected well, therefore you may have to learn to move your eyes to detect something that doesn't move.
Objects that aren't moving appear to move (autokinesis). This has probably led to a number of plane crashes.
If you need to see directly in front of you or see detail you need red. Like many myths the red light myth has some basis in fact. The red truth?
Why red? The center 1.5% of your retina (the fovea) which provides you with most detailed vision is packed almost exclusively with red sensitive cones.
This is the same area that has no rods and is responsible for the night blind spot. There are fewer total green sensitive cones than red. The number of blue sensitive cones is very small compared to green and red.
Which is just as well since the lens in the human eye cannot focus red and blue at the same time. And using green really only changes perceived brightness because of the way the signals are processed in our neural pathways. Unlike a digital camera, more pixels, in this case, doesn't give us more detail."
http://stlplaces.com/night_vision.html