How hard would it be to match window tint?

[jtvang125]

I have a coupe that came with the back and the two tiny rear windows tinted. I want to tint the two front side windows as well. Yes, it's illegal here but I'll take my chances. How hard would it be to get a close of a match as possible? Not sure if it's worth it going to a dozen shops and see how close of a match they can get it.