With the exception of the black woven which has a black buckle, all of the separately purchased bands have a matte aluminum buckle (matches? silver aluminum sport case). There are bands with other colored buckles but they only come matching the watch case if you buy them as one unit (new watch).
That's my SS AW above in the photo and of course at the case you have the colored adapter. When I have my palm upwards and see the buckle you don't see that the buckle doesn't match metals but in this case I'm OK with it. From the side view I don't really notice it.