If you have a piece of paper with red and blue writing on it, and look at it with red lenses at the same shade as the red pen, you see only the blue as black. If you do this with blue lenses, the opposite occurs.
Why not use this to double the page capacity of books? Print two pages where one would now be printed, one in red and one in blue, and you could look through lenses (supplied with the book) and see each page in turn.
Have the entire first half of the book as it would be, but in red, and the other half printed on top in blue, so when you finish one half, you simply switch lenses and go back to the beginning (or perhaps even flip the book over).
The ink would not cost more, I'm pretty sure, as black's a mixture of other inks anyway, isn't it?
You might be able to expand this with other colours, but I'm not sure which.
EDIT: Changed title from 'Two-Colour Book' to 'Two-Tone-Tome' on [po]'s advice.-- dbmag9, Dec 16 2005 I think the amount saved on paper might help even things out if red and blue ink do turn out to be more expensive. Instead of lenses how about a sheet of blue plastic and a sheet of red. Keep folks from looking like they are wearing 3-D glasses.
Of course, I thought this was an idea about a coloring book with only 2 allowed colors.-- PollyNo9, Dec 16 2005 Sorry about the title, any suggestions for a better one would be gladly received.-- dbmag9, Dec 16 2005 two-tone-tome-- po, Dec 16 2005 Wasn't there a pop performer called Tommy Two-Tone ?-- normzone, Dec 16 2005 What happens where the red and blue lines intersect? Do the colors truly stay separate, or does it become dim under both red and blue light?-- phundug, Dec 16 2005 They would mix, so it would probably be black under both, which would still work.-- dbmag9, Dec 16 2005 One could devise a set of goggles with a filter of each color. On flipping all filters up, no light would enter the goggles and the wearer would blunder about. On flipping down one lens (say the green lens) all colors but green would be blocked and one could read the green text. Flip green black up and flip out red, and now read the red text. Next blue, then violet, puce, pink, cornflower, teal and on and on. I propose that thousands of different colored letters could overlay each other, and with enough suitably tinted lenses one could reduce the need for pages by a thousandfold.-- bungston, Dec 16 2005 he drove the bakers van He tempted her with his treacle tarts And his tasty wholemeal bread And when she saw the size Of his hot meat pies It very near turned her head She nearly swooned at his macaroon And he said now if you treat me right You'll have hot rolls evry morning And crumpets every night He knew once she'd sampled his layer cake He'd have his wicked way-- po, Dec 16 2005 Dorothy: Toto, too? Queen Glinda: Toto, too.-- csea, Dec 16 2005 Excellent, though it might be easier to read this with a colored light rather than colored lenses, esp. for those who use reading glasses. With laser light, you could do what bung suggests, have quite a few overlapping colors.-- ldischler, Dec 16 2005 Very lucky.-- dbmag9, Dec 18 2005 You go [po]!-- Zimmy, Dec 19 2005 From a literary point-of-view this might provide interesting narrative techniques. For instance, the same story, told from two perspectives, written on the same page. Rather than having to read red and then blue, front-to-back as the prologue suggests, you can read either, each producing a different take on the same events. A Pulp Fiction kind of intertwined story. An entirely different opinion of the story might be accrued from those who read red first to those who began on the blue.
Nice. [+]-- theleopard, Oct 30 2008 random, halfbakery