How to get warranty on my iPhone?

I bought an iPhone 4 in black from my friend cause she didn't use it at all. I bought it a while ago and she said she didn't have warranty on it or anything. Is there anyway I can get warranty for it?
I also kinda want a white iPhone now. How can I change the color? Or buy warranty for it?

You can pick one up from the apple store, ask an apple employee.

You could only get warranty when you buy it from a store. To change the color of your I phone go on ebay to get different colors.

Its to late for a warrant now sorry, its too old for someone to put a warranty on it. You can only get one 30 days into the purchase date. As for the color you can buy a new front and back phone casing off ebay for around $40. I wouldnt do it tho because it risky and not really worth it.