Programmable Colour Pen

I am thinking that We can make a kind of electronic Pen that has a colour palette control to light up the chemical in different Wave lenght, so as the ink will change colour accordingly.
Will that be a breakthrough in Pen!? Is there any kind of pigment that can react to the light and changes colour according!? So there will be one type of pen in the stationery in future.
HK Snob