I think you misread Apple's web page...
http://www.apple.com/watch/gallery/
(Snip)
So I see 4 different metal accents shown in the Fluoroelastomer band, and none of them are aluminum. In fact, I can't find any aluminum accents on any of the bands or straps.
I didn't "misread" anything, because I never saw any of what you read. Good catch. I was basing that assumption on the look of the... accents/pins/grommets? I saw something on the regular Apple Watch page that simply wasn't there.
Anyway, the more I think about the combinations the more my head hurts. I'm betting Apple will have to "revolutionize" the purchasing process of this is going to work. I bet they'll need an entire keynote just to explain how all this is going to work.