maybe you can try 70% for the front and windshield and darker at back.
the highest heat rejection for 70% i found was V-Kool 70. it has 55% total solar heat rejection.
for the triangle window and rear window. you can try Huper Select DREI, it is a 35% visible light with 70% total heat rejection.
go to V-Kool and Huper's website. call their number and ask where can you find certified installer for their product. They usually reply email within 1 business days.
as for coler, i suggest gray. it is less noticeable and actually increase contract. (you can actually see better with tint film)
這裡有一些車子可以裝和不可以裝的東西
"Tinting the front side windows and the windshield is illegal"