You have a faulty tablet I would say as mine has a perfect screen, no yellowish colour or rainbow effect in mine. The screen blueish effect can be dialled out also using the built in controls and calibration for the white balance.
And you now have three tablets?
Anyway, the Xperia Z3 Tablet is a fantastic device, very lightweight and pocketful, good front speakers, water and dust proof, fast and powerful without any overheating issues. It's also very thin but we'll made. I like mine and am glad I got it over the Nexus 9, but that also has to do with the size difference as the Sony fits in my pocket just.
Perhaps I do but I have yet to swap it out and go through the exchange process due to hearing some not so great stories about Sony's support and an unfortunate incident where Motorola lost a Moto G of mine and never returned or replaced it but I digress, if it weren't for the display issues I have I would love this thing. I'm definitely not the only one though, seems to be pretty 50/50 here...http://forum.xda-developers.com/z3-tablet-compact/general/yellow-tint-t2980301 Maybe I'll play customer service roulette sometime before my warranty is up.
And I actually have 4 tablets including my first generation iPad Air.