What is the best treatment for brown color of teeth?

Tooth bleaching: Yellow and brown color teeth respond better to bleaching than gray colored teeth. Check with you dentist to see what he/she would recommend for your teeth and your expectations

That depends: There are many different causes for "brown teeth". Depending on the cause you might simply need a professional cleaning, or bleaching might help, or you might need veeners and/or crowns. You need to see your dentist to determine the cause and then the appropiate treatment.