G'Day Mark,
The colours are really there, yes. All the filters do is allow the camera to separate one band of frequencies from another - they don't change the frequencies.
The reason it all looks black and white (often

) is simply a matter of light intensity and the sensitivity of the human eye. We need high intensity (bright) light to see colours with the cone receptors in our eyes. In dim light, the cones don't work and the rod receptors in our eyes take over, but the rods only detect in black and white.
Al.