This was actually rumored a VERY long time ago. I'll have to dig it up. Its a cool idea and one that I hope comes to fruition soon. Imagine your computer letting you know you have email by glowing blue, alerting you to overheating by glowing red, or even being able to visually display server load by a series of colors. Besides the aethetic implication of being able to change the color of your case, this is an incredible opportunity to make the computing experience that much more organic.
If you are having a hard time picturing this, go to brookstone and look for the glowing orb. It sits on your desk and glows different colors based on programmed settings (eg. monitors nasdaq and glows green for up and red for down). Also, if you've ever been to Hong Kong, there is a skyscraper there with a brightly lit neon spire. Ths spire 4 colored neon rings for ever hour throughout the evening. For instance, Blue with all four rings lit means 6pm, and for every 15 minutes, a ring is turned off. If you are worried that interacting via color messages will be difficult or unaccepted by the masses, think again. This is the coolest thing since the pulsing LED on power button