[hahainternet]

The comet is in fact very very black, but pretty much all cameras are greyscale. Most 'colour' cameras are just a series of filters placed over the pixels to sense only light of the desired colour (usually RGB)

When science has to be done, it's easier to have a selectable set of filters you can put in front of the whole sensor at once. This way you can use the full sensor resolution and you can have a wider variety of filters. They also tend to bring along spectrometers of some description which are again much much more useful.