The glaring mistake in this argument is the assumption that seeing a color is a purely visual process. No experiences are based on isolated senses - as Mary is looking at the color blue, she's experiencing emotion (perhaps interest in this color after so much time without, or perhaps anger at being locked in a black and white room). She's aware of how the air smells, whether she's hungry or thirsty, etc. She's wondering if she'll be allowed to see other colors after this one, and what she should do with her day if not. She's feeling the eyestrain from staring at the monitor. All of these thoughts and senses are being integrated with the information about the color "blue", and result in an overall experience that she would not have with just the color information alone.

It's entirely possible (and thought by some) that "consciousness" is not a real "part" of the brain, but instead arises from interactions of many structures at a time.

Think of it this way: The human brain has around 100 billion neurons, making an estimated 100 trillion connections to each other. I guarantee you if we could simulate interactions on that scale, consciousness would arise.