Source: ( http://shoutslogans.com/27-great-go-green-slogans-and-posters )
The poster contains an image of Star Wars, Darth Vader helmet but instead of the usual Darth Vader's matt black face, there are two trees. At the bottom, apart from the website it was from, there is also this sentence which says 'Join The Green Side'.
The color of the poster goes well with the theme of the poster as it green in color and green is normally associated with the plants and trees. The black font, tree, and helmet help each one of them to stand out. The black color is also very related to the color of the helmet.
The words used in this poster are ' Join The Greens Side'. I feel that the creator tried to create a relationship between Star Wars and being eco-friendly as they used the famous line said by Darth Vader's Famous line 'Join The Dark Side' but the just changed the color to Green as they intended to deliver the message to become eco-friendly and make the earth green again.
The creator of the poster made the text color 'black' in order to catch the reader's attention. I feel that they are also trying to show what is the main message of the poster so the readers will know that this poster is related to the environment and the condition of the earth.
The words are all at the bottom so the reader will tend to look at the picture first before looking down for the message of the poster.
To encourage them to be more eco-friendly and also encourage the public to do their part to sustain the environment of earth.
to help to sustain the nature and do not let it die away slowly( e.g cutting trees, removing animals' habitats, burn trees for more space)
to help and encourage them to be more eco-friendly