Usually you only bleed the brake system if you are getting a spongy pedal, or have opened any part of your brake system(which usually isn't done when replacing pads or rotors), or if you have low fluid(which usually means something is leaking or seeping somewhere). That browning would concern me a little since steel turns colors when being heat treated/tempered. Are you getting any colors besides brown in there, like purples or blues? I have never had disc brakes turn brown......