The green tent, as far as I know, does not exist. But there is a Blue Tent and Red Tent, received from the Trick Master after completing his final maze. Sorry!
Chat with our AI personalities
The coast emerald is called emerald cuz it is green and emeralds are green.
It is just a different color of the red tent, which is a secret base item that hides you.
You can get it from a person in the lobby of the Verdanturf Battle tent.
The Red Tent is a decoration item in Pokemon Emerald for your Secret Base. There are many places around Hoenn that you can turn into a Secret Base. Note that most bases can only be caves or tree-houses.
Unfortunately you cannot get the legendary dogs Entei, Suicune, and Raikou in Emerald Green. You can import them into Emerald green by trading from Leaf Green and Fire Red.