That's because she was an activist for environmental protection. Green as an adjective often refers not to the color, but rather to describe someone who is environmentally friendly. In this case, her literature fought for preserving the nature and save the environment, so it is therefore green.
The picture showed
Person vs person: this can also mean man vs man but it’s when there are two characters fighting or against each other
Person vs society: this means that one person is against a big group or a angry mob of some sorts
Person vs destiny: this is when a person is going against faint or against what is going to happen
Person vs technology: this means one person against technology or robots, computers, phones, tv, anything like that is fair game for technology.
I hope that helps
