If they are real stone, then well, maybe. Real granite would not discolor due to heat, but it very porous, and will absorb liquids if not sealed properly. Some kinds of stone will also react to acids such as coffee or orange juice. There are products out there that leach liquids back out of the stone, it's a powder you pour onto the stain and then cover and leave for several days, that might work. Of course if it's just water is will eventually dry out on it's own. Once it does look for a good sealer to put on the whole counter top. You can do it yourself, or there are busynesses that specialize in doing just that for you. Find a good tile and stone store near you and go and talk to them, most likely they will sell the products and/or know of someone who does it.