Your paint code should be on a decal on the boot floor, or on the identical decal stuck in the front of your service book, look for a 4 digit code
Alternatively, phone your VW dealers parts department and quote your registration number, they can tell you your paint code, and, if you want, supply the correct colour
If your new grill is in bare plastic, it will need plastic primer, this will significantly increase your spend on paint, and for the sakes of a few extra quid, the Pro job will start to look like the better option! It'll certainly be a better finish!
Thom