Perhaps there is a protagonist who is on a journey, either physical or emotional. And there might be supporting characters that interact with the protagonist, either helping or hindering them. For example, there could be a wise old man who gives advice to the main character, or a rival who creates conflict.
I'm not sure as I haven't read it. But usually, the main characters are the ones who drive the plot forward. They could be ordinary people with extraordinary stories, or they could be more complex individuals with many layers to their personalities.
I haven't read this short story specifically. But generally, when analyzing a short story, we can start from the plot. It might involve a series of events that are linked together to tell a story. Maybe in 'A Curtain of Green', there are unique characters with their own personalities, goals and conflicts.
Perhaps the story is centered around a character who discovers a magical world through a curtain of green, encountering strange creatures and solving puzzles along the way.
I'm not sure as I haven't read the specific 'Behind the Blue Curtain' short story. But generally, the main characters could be the ones who are most involved in the action related to the blue curtain, like the ones who are trying to peek behind it or are affected by what's there.
Since I'm not aware of the 'Green Gulch short story', I can only speculate. Maybe there are explorers as main characters. They come to Green Gulch to find out its secrets. Or it could be an animal character like a fox that is native to Green Gulch and the story is told from its perspective.
It could be about mystery or secrecy. Often, a 'blue curtain' can symbolize something hidden or not easily accessible, so perhaps the main theme is uncovering the secrets that lie behind this 'blue curtain'.
I don't know for sure, but I assume the green bird is one of the main characters. There might also be a person who discovers the green bird, like a shepherd or a little girl.
Since we don't have more details about 'the green door short story', it's hard to say exactly. However, it's common for there to be a protagonist, let's say a person with a sense of adventure and a thirst for discovery. This character would be the one whose actions and decisions revolve around the green door. There might also be an antagonist, although not always. It could be someone who tries to stop the protagonist from opening the green door or someone who has a different view on what the green door represents.
Since I don't know the specific story, I can't say for sure. But it could be characters who are environmentalists if green represents nature in the story, like a young activist and an old - wise tree - keeper.
Without reading the story, it's impossible to say for sure. But it could be a single protagonist, perhaps a young artist who finds inspiration while sitting in the green armchair. Or it could be a group of friends who gather around the armchair for their meetings and discussions, and through their interactions, the story progresses.
I don't know as I haven't read it, but it could be the person who owns the green blazer. There might also be other characters like friends or family members who interact with the blazer - owner and influence the story in some way.