I think Nick is making a good point about the differences between colors as perceived by eyes as opposed to cameras. The camera itself can have different sensitivities to the color spectrum than the human eye. That can have a profound affect on how an image appears. I think the point Nick is making is how the human mind processes visual information. While a camera is an attempt to create an artificial eye, the real processing happens in the brain.

Our brains devote a lot of processing power to handling visual images. It's a massively parallel process that seems to be based a great deal on pattern recognition. This is one reason why we see familiar shapes in the clouds (or the pictures of Mars). We're conditioned to handle different lighting levels and the like without having to think about them.

A camera has no such natural processing. It simply measures different light levels in different color bands and assigns a numeric value to each pixel. These numeric values are radioed back to Earth where people work to reassemble them into images that match the original. Getting the relative values between the color values right has repeatedly proven a difficult challenge on every lander we've ever sent to Mars. In the end, I wonder how much it really matters.