Earlier this week, I was between ordering one of the Z7s and a Ray 35. Ultimately ended up ordering the Ray 35. That said I thought about the Z7 enough to share my thoughts on the colors.
On the Z7, natural is nice because it gets the roasted maple neck. I know this is not a necessary feature, but I like the darker maple color. The downside of natural is that I have seen some pretty horrible grain matching on a few Sire's. If you go natural and grain pattern is important to you, then I would try to get one where you can see the actual instrument you are buying first. That may not be easy to do with these selling out at many retailers.
I like that the purple has a matching headstock on the Z7. I just wish it were more purple and less pink (maybe it is in person?). This is probably the one I would have gone with if I had ended up ordering the Z7, but I am a sucker for a matching headstock.
I am awaiting delivery of a Z7-5 in natural, I think it’s a bit of a crap shoot as to how the grain will be on it and how they match it up. I’m a lefty so viewing before buying is very rarely an option open to me on any bass. The roasted maple neck looks superb against the natural finish, I don’t know why this neck isn’t available on the other colour finishes?