You are blind and your friend presents you with 6 equal balls of which 3 are red and 3 are green.
You friend challenges you to game to find a green ball.
You must select 3 of the balls and your friend will tell you if they are all green or not. You repeat this as many times as you need to until you can identify a ball as being green.

In a worst case scenario what is the maximum number of submissions of 3 balls needed to then be able to identify a green ball with certainty. Assuming you are playing an optimal game. How do you know there is no better strategy?