What are blueprints, and why are they blue?
In brief, blueprints are the architectural plans or drawings, usually of houses but also used for buildings as well. They are also usually used as white lines on a blue background, though I have seem them the other way around, and even with black lines on a white background. EDIT: Also, this site might help, but it was the best I could find. http://www.psrc.usm.edu/macrog/work/blue.
