I've worked it out Michael...it's because a picture tells a thousand words...think about
Jonathon: most cameras these days use red/green/blue celled ccd chips with each cell arranged in a bayer pattern. With twice as many green cells as red and blue. (Because green is in the middle of the light spectrum and we see it better than the rest)
Shooting in black and white or colour doesn't affect the resolution because the cells on a ccd chip don't directly correspond to pixels of an image. Each pixel is averaged from the surrounding cells on the ccd. Whether it then gets interpolated into colour or left as greyscale doesn't strictly effect the resolution of the final image. Taking a picture in greyscale could conceivably be made to increase the resolution though.