Natural green colored contacts for dark brown eyes?

I've been searching for the perfect natural-looking green colored contacts for my dark brown eyes. I am in love with Kristen Stewart's eye color, so if you could show me a contact that looks similar to her eye color i would greatly appreciate it! THANK YOU!!

Here is a good picture of her eye color: http://media.monstersandcritics.com/galleries/admi...

Thanks again!!