So, I am one of those geeks who get JoAnn's discounts (thanks, Andrea, for introducing me to this franchise, I really needed a moneysuck in my life) and yesterday I went to the store to have a look at what wares they offer.
I've bought a couple of books that have "Steampunk" somewhere in the title, mostly DIY craft books that aren't functionally different from most other craftbooks, except the examples they give are things that are labeled "steampunk" which, I have to say, aren't really functionally different from other things either... they've just got a certain shape and colour.
Darice has a line of specialty jewelry called Signed, Sealed, Remembered, and in the beading aisle I found a string of the usual suspects: gears and sprockets. (They are from Blue Moon Beads, if you must know. It's quite necessary, in my line of work, to keep track of brands. It makes re-ordering things easier. And, it also tells me as a researcher who is generating the items we are commonly using in our DIY, and allows me to extrapolate on why by comparing to the rest of their merchandise.)
(Aside: really do check out the Darice stuff, because they are really cool in terms of customizable jewelry! You can stick anything you want on the pendants and you're not limited to what they think you should have as part of your identity. It's super neat if you are the kind of person who, like me, think that customization really ought to be as much of the crafter's input as possible. Ah, it's so good to be a geek.)
In all my shopping, steampunk stuff sold at craft stores come in pretty much three colours: brass, copper, and silver.
It's easy to see why brass is so common. It's kind of a dirty yellow (read: gritty) (maybe it's a gritty-looking gold), and I'm going to keep collecting these brass-coloured things, because it seems most of them are printed in a way that it looks tarnished. Amy Sue Bix has got a great article on steampunk aesthetics (versus Mac aesthetics) where she reminds the reader that we like this old stuff because it gives us a sense of the long-lasting, the permanent and thus the reliable, much like how the Victorians, when they first started using trains, built train stations using Greek columns, so that the general public would feel safer using that newfangled technology! But I've also seen polished brass being used (especially on props!). It's too bad these things are only coloured on--I have a wonderful pouch belt with brass-coloured buttons and studs, and you can tell which buttons I'm constantly opening and closing because they look silver now XD
Copper is another common colour. It's one of the materials in brass, so, duh. It's also good for conducting electricity, which, yay! It's an interesting colour: it's not a straight-up brown, but a reddish brown... or perhaps brownish-red. Like pennies. It's a very common material! You find it everywhere, which accounts for part of why it's in steampunk so much. (There's not much in steampunk that you can't find anywhere else.) Like the brass, copper steampunk stuff, sold in retail, always looks vaguely tarnished.
The red-brown of copper also looks like rust, with none of the nastiness of rust, so, yay. Which adds to the "looks old and solid and hasn't disintegrated into dust yet, woo" impression.
Silver is the least common of steampunk colours that I've found. I'm partial to it myself so I always notice it when it's there, but it's not as widespread as copper or brass. Part of it is that sterling silver doesn't really look great when it's tarnished. Another part is that sterling silver is actually really expensive so most of the stuff on the market is probably not actually silver, which means when it tarnishes, it goes weird. I've had really nice silver-coloured jewelry that went green with white, and then black as if an ancient curse took hold of them.
I think the other part of why it's not as common is that tarnished silver isn't a commonly attractive colour. (Only steampunks care about it, maybe?) And it is a strange thing too. I remember I had a raygun which I spray painted silver. When I showed it to a roommate, she said, "you could rub some black paint over it to make it look tarnished and older." There is a fetishism on things looking old in steampunk which silver does not really lend itself to as easily as the other colours. (And really, if you have a silver raygun, why would you let it tarnish? Taking good care of your weapons, even if they are fake, ought to be a thing, no?) And a tarnished silver rather looks like steel, which isn't quite so steampunk anymore!
These are just the colours of the metals in steampunk, not accounting for the actual variety of steampunk costuming. However, when we say "steampunk is when goths discover brown" it's pretty interesting to ask what it is we're trying to reflect with the brown colours besides sepia colours. Do we stick to browns because we're trying to achieve the sepia palette of old photographs? (Which doesn't account for the coppers.) Is it because browns are so easy to mix-and-match with practically any other colour? (Try it! Which wouldn't account for people whose steampunk wardrobes are literally ALL black, white and brown. MAYBE green, but usually that dark army green. I know y'all're attached to your khakis but come ON.) And when it comes to craft store merchandise, are we as consumers really creating the demand for these specific colours or are they selling us what they think we want?