Computer monitors, like TVs, are based on the red, green, blue (RGB) color model -- they generate light in those three colors.

Added together, those three colors produce white light, and in different combinations generate all the colors a monitor can display, which is some subset of what the eye can see.

Printed material, on the other hand, uses a set of three colored inks (cyan, magenta, and yellow, or CMY), each of which reflects a certain part of the full white-light spectrum, and which in combination produces black. (In practice, the three ink colors are usually supplemented by a true black.)

The CMY color model can reproduce an even smaller subset of the colors they eye can see, and a challenge for computer-using designers has always been to get their monitors to properly display printed colors. That's what the whole color management/ColorSync/profiles technology is designed to address -- converting images from one color space to another accurately.

Now Apple has taken a more direct approach, by patenting a display technology that uses filters to reproduce images using the CMY color model rather than the RGB model. "As a result," reads the patent, "color shifts, for example, can be more reliably reproduced between the display and the printer,"

There has been no discussion of plans to actually manufacture such a display, however.