Generally speaking Gray Install Discs are Machine specifific, but sometimes work on a Range of Macs released at the same time.
The 10.6 Reyail Disc is incredably cheap for an OS disc though... $29!
Snow Leopard/10.6.x Requirements...
* Mac computer with an Intel processor
* 1GB of memory (I say 4GB at least)
* 5GB of available disk space (I say 30GB at least)
* DVD drive for installation
* Some features require a compatible Internet service provider; fees may apply.
* Some features require Apple’s MobileMe service; fees and terms apply.
Which apps work with Mac OS X 10.6?...
It looks like they might still have it...
If it's a core Duo & not a Core2Duo, then it'll only run in 32 bit mode.