A theme is a central topic,subject,or message within a narrative.
Affect is a verb that means to influence something and effect is a noun means something that is or has been influenced. I'll use them both in a sentence. "She was affected by stress." "She didn't like the effect stress had on her."
Now for grey and gray they both mean the same thing. They both refer to the color. Gray is just the more popular spelling in the US and grey is more popular in the UK. You can spell it however you'd like.
Hopefully that helps!
The formula for area of a square is (P/4)2, where P is the perimeter.
The answer to this simple questions is A