4/C & Then Some :)

Nature and it's inherent connect to tech never ceases to amaze. Back in the day, yours truly was a corporate identity designer using 4/C printing (CYMK - Cyan, Yellow, Magenta & Black/K - used to enhance the printing process) to produce annual reports and ad supplements for companies as CYMK enables printers to recreate the full color spectrum without issue whether the print process be inkjet, offset or rotogravure. Correspondingly, as described in the Physorg piece, four colors were also used by cartographers because...

four colors are sufficient to color different countries on a 2D map so that no two adjacent countries have the same color (excluding intersecting corners). 

Now it appears researchers use the same centuries old approach to manipulating color to better understand the nature of crystals.

Now, a team of mathematicians, physicists, and chemists from the US, South Korea, and Japan has discovered that the four-color theorem can be used to understand the crystal structure and magnetic properties of a complex material. Their paper is published in a recent issue of the Journal of the American Chemical Society.

"Most technological materials such as steels or magnets exhibit complex domain structures, which often determine macroscopic physical properties," Sang-Wook Cheong, Professor at both Rutgers University in Piscataway, New Jersey, and at the Pohang University of Science and Technology in Pohang, South Korea, told Phys.org. "Our paper, for the first time, demonstrated that the configuration of domain structures can be understood in terms of mathematics, specifically color theorems.

Seen below is the RGB (Additive colors - used for video) and CYMK (Subtractive colors used for print) diagram set showing how colors interact to generate the full color set populating every image output device known to man. Note: K - Black is always used in quality printing as subtractive inks are "dirty", thus requiring black to enhance the printing process. :)