Your concern is very common these days and can be solved easily. Amalgam fillings were used in old days when there was no tooth color filling material. In modern dentistry we use Composite fillings (color matched to patient's teeth colour) to fill cavities. Simplest solution is to replace the old filling with the composite filling to match your tooth colour. As the filling colour will exactly match the teeth colour, one will not be able to make out the difference between the original teeth and the filling.
Schedule an appointment at dent-inn to solve your problem.