My powdercoaters say there are issues with doing two tone. That means you have to bake on two different colors, and since its a hard plastic coating, there may be a seam between the colors for water to get in. I suspect automotive paint is the way to go if you want two tone, or a base powdercoat, withe the second tone layered on top in automotive paint.

I totally agree with the powdercoat choice. When all is said an done, its a Miyata tourer, not a Mario Confente. They'll fetch a good sum in the right condition, but that means near mint. Its essentially just a beautiful and very well made steel touring bike that was made to be ridden the crap out of. The reason they fetch so much is, at least in part, because few touring bikes of that quality are made today, and the ones that are (see rivendell, and that's very debatable. I think the Miyata is better) cost quite a bit more. Think about it like that, and you'll see that its really a cheaper (and much better) alternative to a more expensive new touring bike.

If thats the market, then as long as you keep the frame straight, there will always be a market for these bikes. They're utilitarian and exceptionally made, and that is the value of the bike much more than the paint. Get it another fresh powdercoat if you ever sell it - why would you do that? better to keep it in your doomsday kit - and you'll still get some good coin from somebody who wants to tour, no matter what.