sadly that is a problem when having your wheels powdered, we've had a fair few sets done for customers and all we do is look through colour chips to find a good match, it will never match 100% as the powder laquer doesnt have the same gloss as what we use, luckely most of our customers either go for a gunmetal grey or satin silver so we tend to use the same colour alot, yours looks a little darker to what we do but vauxhall and alfa romeo colours both seem to be good matches. try a local bodyshop and see if they can match the colour for you