Do these always have a matching color hammer & trigger?

While I have never seen a "new in box" example with a mixed color hammer/trigger combination, S&W is known to be very "frugal" in terms of usage of parts when needed. So, I wouldn't use the term "always".

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Ret. LE, FA Instr, S&W Armorer

Typically, yes they match.
There are numerous 3Gens out there from police turn-in that have been properly serviced. Doesn't make them bad, but the finish detail of said parts may not match perfectly. The bead blasting can vary on some batches of parts too.

I had noticed that one on an auction site had a black hammer & all the rest on the site had stainless ones.