this is one of my pet peeves, like when someone has black bridle & a brown saddle. or like a brown saddle w a black girth. however, it really doesnt matter in the schooling. but i ALWAYS ALWAYS ALWAYS, like to have matching tack in the show rjng. you put more put together and professional.
This choice is mainly up to you. Personally, it is okay to ride with different colors during schooling, lessons, and even shows. If it really bothers you and is noticeable during shows then I would consider replacing the bridle. Otherwise I think its fine.
Most people would reccomend that yes, you should have matching leather tack as it's the more "traditional" thing to do, but if you're only lessoning/schooling and not showing, there's no need to change it. If you were to show however, you probably should but I don't think it's required.