"The fruit is green."
Translation:La fruta es verde.
Generally, ser = permenant to be. While estar= temporarily to be. That is why someone asks "¿cómo estás?" instead of "¿cómo eres?" because feelings change a lot. Also why you say something like "Esta manzana es roja" es is used because the apple is most likely to stay red for its entire "life".
I think both are correct but have two different meanings. La fruta esta verde means that the fruit is not ripe (it is still green). The verb estar talks about the state or condition of the object. La fruta es verde means that it's a green colored fruit like a lime. The verb ser (in this case "es") is used when describing the characteristic of an object.
Most feminine words end with "A", and most masculine ones with "O". Keep in mind I said most, not all.
The link above is useful, but I wouldn't ever click directly to a link from a comment, it might not be safe. Yes, I am telling you not to trust me, or any other "person" you might find here that you've never met in person. Instead, google feminine vs. masculine Spanish, and find it there.