Question re buying mac OS software

[*old-guy*]

Hi Guys,
I hope it's OK to ask this question and that it doesn't contravene any sort of Piracy rules.
I want to buy some version of OS X for my Mac. (see the specs of it at the bottom) I have my heart set on Tiger but maybe my wallet will say that Panther is good enough, lol
Ebay has loads of Mac OS software for auction but how do you tell if the software will work on my system and not just the exact Mac it was made for?
Did I read somewhere that the colour of the disc is important?
BTW, I'm not talking about a CD-R copy of an original disc (or 3) I mean an original set of discs that the seller no longer has any use for.
Cheers,
Steve
__________________
PowerMac G3 B/W @ 400 Mhz, 512meg Ram and 12 gig HDD running OS 9.2.1 but slowly working on upgrading it.

 

[siurpeeman]

since you have a powerpc mac, then any retail copy of mac os x should install fine assuming your machine meets the minimum requirements for installation (don't know what it is for tiger/panther). just make sure you don't buy re-install discs that came with someone else's computer.

 

[0007776]

If the disks are grey and have the name of a particular model on them they are not the ones that will work on any system. The retail ones are black. And if you buy tiger just remember that it comes on a DVD so you will need to have a DVD-ROM drive at least.

 

[*old-guy*]

Thanks, guys.
Just knowing not to buy the grey ones makes the choices a lot simpler.
Yes, my Mac has a DVD and meets the rest of the specs so Tiger should be fine.
Cheers,
Steve