Don't get green or any other color of contacts. Colored contacts don't work well with really dark eyes--it always comes off looking kind of demonic and fake. If a person can easily tell you are wearing colored contacts and it doesn't look natural or normal it usually does not look good...and I have never seen anybody with dark eyes pull off a good eye color change.
I have blue eyes but I know this guy with the most beautiful dark brown eyes. I always want to look at them!
Ok sorry back to the question! I think all eyes are gorgeous and me having blue eyes I sometimes want brown eyes because they look so deep and just plain pretty. I have looked at getting colored contacts before but the color didn't look that great so I decided against it. And I saved some money too! So you should just love your dark brown eyes(that I do not have)! If you want to get contacts that's your choice I think your eyes would and will be beautiful either way:)
I think brown eyes are really pretty, I have thought about getting really bright light blue ones before for a change but they are pretty expensive and I chose not to but if you fancy a change why not. I still think you should stick with your natural eye colour though :)