I completely agree with Eamon, that English is a strange language. If you want a definitive answer, when you say"it is kind of you" that means that the person is doing something that you find is kind. When you say "Its kind for you" it is as if you are asking them to do something. That is how I perceive it, and I am a native speaker. Hope this helps!

English is king of strange, I'm a native speaker and I don't even really know how to answer you. The first one is "correct" but someone will understand if you use the second one.

"It's very kind OF you to do me a favor" (we would say this) "It's very kind FOR you to do me a favor" (we would NOT say this)