What do you study at college?
What are you studying at college?
It seems to me that in 1 it can mean a generic YOU. Hence, 1 can mean "What does one study at college?"
In 2, it is more a specific you. I am asking my interlocutor what they are studying at college.
But on the other hand, they may mean the same with the meaning of the sentence 2.
That's what I think. Tell me what you think. What difference can there be between them.