Quote Originally Posted by RPMiller View Post
So did TSR really produce those maps in nonphoto blue to prevent xeroxing [...]
Yeah. For similar reasons, they did many runs of the official AD&D character sheets on paper with a fairly heavy orangey-browney background that was difficult to photocopy (without great care it would produce a muddy swamp of grey mess), and in some later things they used red screens for similar reasons, since red photocopies as almost-black.

I'm just glad they grew out of their "Blue Period" in time to do awesome maps like the I6: Ravenloft plans