See through is a way of saying a material that lets all colours of light through. It’s not so much a colour as the absence of a block to coloured light.
That’s a deep philosophical question. Are we just models in a computer simulation, are we real, who knows? I don’t know. I took a philosophy class last year, that stuff is waaaaaaaaay harder to get your head around than science.
See through is as Triona says just the fact that a material is not reflecting any light back to you, its allowing the light the pass through as opposed to a red rose which absorbs all the other colour wavelengths and only reflects the wavelength of red back to your eyes.
I think the question your asking is known as solipsism. The fact that you only know your own mind exists and everything else is uncertain. Is everything else a simulation or are you part of the simulation itself. If you’ve never seen Blade Runner, do yourself a favour and watch it. Its all about advanced robots called replicants that don’t know they’re human and Harrison Ford is a bounty hunter who tracks them down and kills them if they get out of line, but who is and isn’t a robot? Can anyone be sure. Really great Ridley Scott movie.