I was watching the Maze Runner again and When Newt had called Thomas the Greenbean, what did he mean by this?
The colour green symbolises new or fresh or inexperienced, what it means is that Thomas was new to the Glade and inexperienced. Bean is just a catchphrase to rhyme with Green.
The colour green was used in comparison to Thomas being a 'newbie' and the bean bit was because that was the start of his journey when he arrived there. He grew from then on.