The sound card connectors are hopefully colour coded too. And, hopefully, using the same code.
Are you sure that your card supports 5.1 sound though? If not, the colour code wont really help, as it may be different.
My 4.1 system has 2 plugs, green and black, that go into the sound card (they are front and rear, but not perhaps in that order)
These go from the sub(woofer) to the sound card. The satalite speakers all plug into the back of the sub.
The plugs on the back of the sub are labeled front right, rear right etc. It's just a case of putting the satalite speaker in the position the label on the sub says for the plug the satalite speaker is plugged in to.
hope this helps.