just to put a newer post here, I have a June 2019 model 3 and a new Jan 2020 Model S.....I had the M3 tinted with 3M Crystalline 70% on windshield, 50% drivers and passengers window, 40% top and back windows.....it looks great.....
My model S has the exact same tinting and does not exhibit any of the “purple” colors....it is very much a duplicate ope my M3.
I did them at different shops......both 3M certified and both did a super job.....Since a lot of these post were 18 to a couple years, I think the 3M product has undergone some changes to film that eliminated the so-called "purple effect” and the Tesla window glass has probably changed also....point being, currently I have this product and am extremely pleased....the 70% on the windshield is almost clear and my installer has given me a ticket warranty in writing that allows me to have them take it off and re-install for every ticket I get at no charge....
The heat is the first thing you notice that is reduced.....I almost used Xpel Ultimate Plus.....a very good film but is much more expensive than 3M.....also have C-Quartz Finest for ceramic coating......good combination and cars look great