Rear speaker fitting

I've got some rear speakers since my Clio didn't have any. One question is how do I know which wire to connect to the positive and negative terminals on the speaker.

The Clio has a purple and a grey wire, or does it not matter?

Also am I right in thinking you have to cut one of the terminals off to fitter a bigger connector on for the positive speaker terminal?

Sorry bit of audio novice! Quick reply would be awesom!
 
you can buy a renault to speaker link on ebay, plugs straight into the connector and will have the small and big spade connectors on the other end.