When any titanium exhaust system leaves our workshop, they are produced in a brushed finish with silver looking welds (unless you chose to have it black!) We never let our systems leave the factory with colour! This kind of finish would mean the welding process was incorrect and the welds we put so much pride in would be weak and brittle.
Over time and through consistent use titanium will naturally change to a more colourful version, this is created by heat generation and the chemical reactions that occur in the material.