[mercuryrising]

Whoops, that should have been translucent. Yeah you tune the gold nanoparticles to absorb radiation that is able to be transmitted into the body (I can't find any graphs of the human body's vis/ir transmittance - although water is a good 'baseline'[1]). Tuning something to green wouldn't work so well, because you can't get the light in. But infrared works great - evidenced by how readily red light passes through fingers with flashlights.

[1] http://en.wikipedia.org/wiki/File:Absorption_spectrum_of_liq...

[dTal]

That still makes no sense: 1) light itself cannot be transparent or translucent, only objects, and 2) the human body is in fact opaque in the infrared, as evidenced by the fact that heat lamps warm us up.