I don't believe we actually know their "ink's" mechanism, so it could be ChoLCD (which I think they've gotten to pretty quick response times, but it's been a while since I looked at them).
Yeah, they are only talking about having made the electrodes and wires transparent (or at least not visible), but if they couldn't make the inking agent similarly transparent, it would make a really crummy addition to a car's windshield, for instance, which was one of their own examples. So I'm thinking they probably have "ink" that vanishes too.
I could be wrong, now, but I don't think so. (That one's for my fellow
Monk fans out there)