Never heard of it
before, asked our supplier nope never heard of it.

Been trawling the
web for it, still not come across it yet,

as you mention it
could be heat sensitive inks or possibly  plastic, maybe they could
be  utilised.

may take a bit of experimenting
to get the desired affect.

here's a few
websites/ companies that may be able to help:

http://www.freepatentsonline.com/5928803.html

http://www.teachersource.com/catalog/page/Color_Light_Sound/Liquid_Crystal/?id=bed55765b60c0fe99daca7e1138bcde2