For the most part, Amazon (and Dell) only stocks one color for each Nokia device. The only other time that I've seen differently is for the E71, when both the gray and white keyboard colors were available. And that's about it.
Sure, due to its penta band RF radio, you can likely buy an N8 from overseas and import it. Of course, the huge downside is that if you get a defective device or you're just not happy with it, you're stuck with it, no returns/refunds. And from what I hear Dell's return service isn't great; you get hit with a return and re-stocking fee. Stick with Amazon and Newegg.