You can made a reflective coating for a single wavelenght, i think with +/- 10nm precision, or also a bit more, using holograms printed on the lens ..... usually, holographic optical elements matched for specific wavelenghts, are visible only at these wavelenghts, and almost invisible with other ones (as example, the mirrors made for HUD displays in the hunting airplanes, that are holographic mirrors ..... completely transparent for all the wavelenghts, and reflective for the color of the displays) ..... probably in full sunlight it appears as a normal CR lens, maybe just a little pink, but almost unnoticeable, where instead if illuminated only with a green laser, they appear completely black (i have a very small anti-IR filter, made with this holographic system ..... at eyes, it's perfectly clear, just seem very light AR coated, but looking at it under IR light with a camera, it appear totally black)