Decide on a paint shade, then nip down to your local paint store. Ask the guy what colours are in the Nissan GM paint (there will be various tints added). Then chose one of the tints, and get that added to the base colour. That way on sunny days, the metallic hues will match.....
Did the same with my old Evo - paint tint from Mitsi silver (which is blue) added to gunmetal paint - worked a treat.
Once you start thinking about polished lips and such - the costs spiral....not to mention the hours keeping them tip top.