My car is silver. I have pretty much 35% films pretty much all around. And they definately sharpened up the look of my car.
On a sidenote, if you're gonna have your rear window tinted, there are a lot of times that window films will not stick completely on the top portion of your rear window. It's b/c there are tiny dots ("dot matrix" above your defoster lines) that make them difficult for the films to be applied completely w/o having air in between them. Even highly skilled filming professionals have tough time working on those sections.
I have a black vinyl on that section, which the filming shop suggested me have it, and it worked really well. It also works as a rear window visor, too. (It is on the interior side of a window, just like window films. Not on outside tho.)
GL w/ your decisions.