Originally Posted by TrAI

You could have a camera capable of taking RGB pictures, but you would still have to find out what to think of as true color for calibration... And of course, it would have many disadvantages... The most important would be that the channels of the imaging would not utilize the full grayscale range; one would have to maintain either the absolute intensity of all channels or the relative, so you would loose detail compared to grayscale optimized images. This reduction in grayscale resolution is not easy to undo by post processing the image... This has been discussed on several earlier threads.