Ok, I did a couple of searches on this and am still not satisfied. I have polarized sunglasses. When I look at some GM (think Pontiac minivans) vehicles, and some MB vehicles (less pronounced effect) with my sunglasses the windscreens look purple. After you see it you can sometimes see (although much less obvious) the purple color without any polarization. Doing a quick search online gave me no credible reason this happens. I think it has something to do with a UV filter, and some partial polarization but I have no idea really. The only thing I found was people asking the questions. I am sure it has something to do with the glass prep. My question is does the Model S have a purple windshield (when viewed with polarized glasses)? Does the pano roof, or back glass have this effect (possibly due to a UV/IR filter)?