Architects seem to love white. Most homes have white siding or trim. Most traditional buildings use limestone or a white marble. And, although modern buildings are largely glass and can choose an unlimited range of colors for the paneling and mullions, a surprising number go with white or a "white" metal like brushed aluminum. However, when it comes to representing the white surfaces of buildings the reality is that nothing is pure white. Artists throughout history have known this intuitively, avoiding pure white, and instead dancing around the light blues, pinks and lavenders that you actually see.
Actually the picture that got me thinking about the color (or non-color) white was a picture of a statue in the Wall Street Journal (March 24, 2012). The Dying Achilles by Ernst Herter is carved from white marble, but the photo that was printed was dramatic and very colorful.
So, getting back to the problem of architectural reality and architectural illustration, what is going on here? The human brain learns early on that the raw visual data that it receives from the senses mean different things.