The FADER called it. LA Times called it. Random blogs have called it. Just like gold and fluorescent are the new black, hypercolor clothes are about to replace acid wash jeans as the nerdiest textile. It's about time! What's more stylish than wearing micro encapsulated PH indicators?

I guess I'm kinda fashionable but I was never on top of the hypercolor fad of the 90's. If only I had realized the chemistry involved in these garments I'd probably be dressed in a hypercolor unitard through public school.

How does it work though? Gordon Nelson gives you the summary in his paper "Application of microencapsulation in textiles": 

There are two major types of colour-changing systems: thermochromatic which alter colour in response to temperature, and photochromatic which alter colour in response to UV light. Both forms of colour-change material are produced in an encapsulated form as microencapsulation helps to protect these sensitive chemicals from the external environment. Today manufacturers are able to make dyes that change colour at specific temperatures for a given application, e.g. colour changes can be initiated from the heat generated in response to human contact.

Wikipedia breaks down the science, albeit unsourced, in greater detail:

The liquid [inside the micro capsules] is a leuco form of a dye (in this case crystal violet lactone), a weak acid (1,2,3-benzotriazole), and a quaternary ammonium salt of a fatty acid (myristylammonium oleate) dissolved in a solvent (1-dodecanol). At low temperatures, the weak acid forms a colored complex with the leuco dye, interrupting the lactone ring. At high temperatures, above 24-27 °C, the solvent melts and the salt dissociates, reversibly reacts with the weak acid and increases the pH. The pH change leads to closing of the lactone ring of the dye, which then regains its colorless (leuco) form.

At least it should tie me over until the wearable computer fad comes back into style...