I'm not sure if Greg is offering alternative colours via the sample pack. From my discussion with Sam, I got the impression that he's ordering a few hides to try.Graemsay mentioned that other colors are available through the sample packs, check about his posts above. I would go with a color that is not offered by Aero at the moment, to get the most out of it. Japanese brands like Mushman is doing the grey, prunga (cordovan), and that blue.
Then again, if you asked for Prugna (which looks completely awesome), I'm sure that they could tag it to the order.