In this infographic, Stephen Von Worley observes that the number of discrete colors in a box of Caryola Crayons doubles about every 28 years. That's an annual growth rate of 2.56%. Von Worley writes:
If the Law holds true, Crayola’s gonna need a bigger box, because by the year 2050, there’ll be 330 different crayons! Shortly thereafter, frazzled packaging designers rejoice, for to the rescue comes a revolution in household appliances: the new-fangled Replicator-Dissociator! Load it with the Crayola plugin, and you’re seconds away from every shade in the rainbow – no boxes required!
Link via Make
I think by the time that sort of technology comes, everyone would already be using e-paper....
Note that there's a typo in the article: "Caryola".