With how mostly green your colour palette is, I think there's great potential to create a very strong design language with your players. By using specific colours to mean very specific things in gameplay, and in the story.

1. But I also agree that it can be nice to keep the mostly green colour palette as a style. A little bit of colour here and there can make certain scenes just pop more pretty, highlight important gameplay elements, add to the story through metaphor, or just making stuff less monotonous.