Iphone 4 screen not working, can i get it replaced or fixed at an apple store?

I dropped it, and there are no marks on it at all.however, the screen is black and blue and there's no image. But when i go to "slide to unlock", i can hear that it works.

If its under warranty 1 year

Yes you can get it replaced via apple service center and tell them that it gets while i was operating the phone, it suddenly turns into blue and black. Don't tell them that it was dropped or was your fault, then they will not replace the screen. And yes if the phone is in warranty then they will replace it for free otherwise they will charge you.