If All Else Fails:
You can usually get a very good match by mixing your own from Testor's Pla hobby paint. Pla is what people who build models (car, airplane, etc.) use. Any hobby shop will have a selection, and so do most KMarts. For metallic colours, begin with silver, then tint it lighter with white, or darker with black, or put blue in it- whatever you need to match the colour you want.