Well as it turns out it looks like by sheer luck, I now have both a "silver" and a "champange" U-3PO so I'm good.
Here's the weird thing - the "silver" one came out of the set of figures I picked up at WalMart this week. My "champange" one came from the case of figures I bought online, and had for almost a month.
So which version came first? The info on that otheR Site forum indicates that the "champange" color pieces came from WM while his "silver" piece came from Target. In contrast, my entire "silver" figure came from a set purchased at WM.
So I have to wonder if there is any rhyme or reason with regards to the coloring. One thing is for sure, if you're not lucky enough to find this entire wave all at once, open up the figures you find first and then bring them with you while you're shopping so you'll be sure to pick up all six pieces of the same tint.