I've got some projects where I'd actually like to maximize and control the
surface coloration. What I can do to make it as pronounced as possible?

clock hands are blued in this manner. Willian SMith, a famous clock maker
suggests to put the hands on a bed of brass filings collected from the
lathe or band saw and heat then on the stove top until they turn blue.

The metal must be clean because you are dealing with oxides and you
want the metal to all react at the same time. Therefore the metal must
be clean and uniformly heated.

chuck