The idea is that you can use this pen to point at any object in the world, the pen then ‘extracts’ the colour, and then is able to write in that colour using a mixture of RGB inks that it contains.
Unfortunately, it’s just a concept, designed by Jinsu Park.
As far as I know there are no practical implementations of this interesting idea. One could make a strong argument that the pen should use CMY (or even red, yellow and blue) primaries since RGB primaries would result in a tiny colour gamut and wouldn’t allow the pen to reproduce any real colours at all. See http://colourware.wordpress.com/2009/07/08/what-is-a-colour-primary/