Condensed milk, due to it's high sugar (preservative) content, doesn't need to be cooked to as high a temp as evaporated milk is. Because of this, it should be whiter, at least in theory. You find a lot of tan cans out there, though. Most of the time the color comes from overcooking, but it can also be a result of age, I think. It's perfectly fine to eat, though. In fact, you'll get caramel flavoring that you won't get with the white stuff. In essence, it's halfway to becoming dulce de leche.