Metals - aluminium and?

As a student I designed a bangle/cuff made out of thin guage brass
and copper in a weave type design. At the moment I am trying to
develop the design to produce in quantity as my first sale piece.
As I will only be dipping my toe in the water and don’t know how
well it will sell it is important to me to not spend up big on the
initial material costs.

For this particular piece the value is in the design whether or not
precious metals are used… I am wanting to find a combination of
two differently coloured metals to use for the piece. A high
priority is tarnish resistance. I have in mind to use aluminium as
one of the metals - I have only used aluminium once before in
jewellery - I know that it is soft and scratches easily and am
wondering if there are any other problems with it that I should know
about before I go ahead and use it.

For the other metal I was thinking perhaps coloured titanium… of
which I know nothing about - I have never used titanium in
jewellery. I have always assumed that titanium must behave
similarly to aluminium as this is the impression I got whilst
watching my friend work on a titanium piece years ago.

I am also curious about gunmetal - I am wondering if this would also
be an option. In my research so far I have turned up very little
about it. What I have found out is that it is a brass
alloy - would this automatically mean that it is not resistant to
tarnish?

Tarnish resistance is a high priority mainly because this piece sits
against a large area of skin and I doubt I would get repeat business
from customers who end up with big green patches on their skin after
wearing the cuff. Also, I am intersted in avoiding any metals that
a large percentage of the population has an allergy to - the only
one I know of so far is nickel.

Thanks for any advice you can offer.

R.R. Jackson