All of the variations are occasionally for sale on our sales forum. You can also find them in online auctions but they are usually priced higher there.
You can go to spyderco's site and see information on all of the sprints and dealer exclusives (there is a slight difference between "sprint" and "dealer exclusive").
http://www.spyderco.com/exclusives/
My understanding is that there won't likely be any new gray or orange models produced but they are available on the secondary market. There are a few knife dealers that have or might have new brown ones available. I have heard rumors that the dealer that commisioned the blue ones is going to have more available later in the year. The last sprint run that was announced but not delivered yet is the green para 2. Nobody really knows when those will be available but theoretically they are already all sold out although they will also show up on the secondary market. All of the PM2's are nice, even the standard black or digicam models.