I'm not sure. Hubble, for instance, doesn't actually take color pictures, but has filters that only allow certain wavelengths of light through. By analyzing and combining data from different wavelengths, and assigning colors to wavelengths, color images are produced. Cassini's cameras work in a similar fashion. That said, this method does allow them to produce "accurate" colors as they believe you'd see if you were actually there viewing it.
Right I knew the gist of how it was done. I've always wonder if the images were totally accurate though, and not over saturated or what have you. I wish they were able to take a "true" picture instead of putting composites together from the different spectrum.