Comment by kurthr

That depends. For ITO it can be quite transparent (80-90%), if you do a good job of matching the index of refraction (otherwise you get weird yellowish reflections and blue transmission). For the nanotubes and metal mesh, it looks fairly neutral (grey >90% transmission), if they do a good job darkening the metal so it doesn't reflect. The OLED meshes are only 2-3um wide and actually aligned with the display sub-pixels (to allow their light through) and their reflections are blocked by circular polarizing films which help make the display black as well.

Just for clarification, the reason that ITO can be transparent even though it is conducting is due to a fairly novel effect where the bandgap of the material is just wide enough to allow most visible light (red-blue) through while still allowing electron conduction (degenerate bands due to Sn doping?). It's pretty cool. Most conductors (metals) have conduction bands that reflect visible light (though they might let X-rays or IR through). Most transparent materials (eg. glass, water) are insulators which have wide band gaps, but no conduction carriers (electrons or holes).

One counter example is Ruby (chromium doped sapphire) which looks red. If you heat it up the bandgap narrows and you it turns dark/black because only IR can get through, while if you cool it in LN2 they will turn light pink as the bandgap width increases!