How much more information is encoded in a color image

Each wavelength corresponds to a different (spectral) color; thus, there are an infinite number of colors between 400 nm and 700 nm, our visual range. Furthermore, most objects have colors which are mixtures of different spectral colors – for example, purple results from a mixture of red and blue light.

a. By what common mechanism do color TVs and computer monitors, color film, & cheap color printers produce the huge range of colors that they do? Hint: your eye senses the infinite number of colors by a similar mechanism!
b. How much more information is encoded in a color image than in a grey scale one? Explain.