Polarizing filters really don't do much at night. They work best at reducing reflected/refracted light.
Most cameras are 24 bit color, regardless of pixels. 8 bit per color channel. Really not that great when compared to film, which is the equivalent of around 256 bit.
What you are seeing is increased color saturation because of the longer exposure. If you look at the high and mid tones, they are mostly washed out, showing that the color depth really isn't that great.