It would be cool to print out a black-and-white image on, say, a laser printer, which contained an unobtrusive embedded "watermark" or "barcode" that contained chroma information for the image --- rather like what the Apple II did to get NTSC color just by producing a pattern of 1's and 0's.
This works for NTSC because the color TV people needed to place their signal on a backwards-compatible black and white signal, so the I and Q information is squeezed into a narrow band just above the Y -- and hence high-bandwidth luminance patterns alias into the color range.
Come to think of it, the Apple II scheme turns a well known broadcast bug (there are dress codes for on-air appearances, as houndstooth and similar high-frequency fabrics alias into color) into a feature. I wonder how much the use of gradients in web graphics is due to recent-featurism, and how much is in imitation of broadcast graphics, which have to have smooth gradients -- they'd bleed if one tried to make a crisp transition.
Then you could point, say, a cellphone camera at the image, and push a button, and see the image in color.
Unfortunately (fortunately?) the information between a cellphone camera and a printout isn't mediated by NTSC, but by regular photons, so it seems unlikely this would work.
-Dave
