Enkei refuses to sell customers touch-up paint in its "secret recipe" colors. This is a lost revenue opportunity and pisses off their customers.
So I searched around and found this touch-up pen in a 99% match for Enkei Gold, see pics below. It's an old Subaru OEM color. Pen costs about $20 shipped. It's crazy how much enkei's paint color appears to shift based on lighting conditions.
Every paint vendor has their own blends, some match better than others. This particular one is really close. YMMV!
link:
http://www.2-tip.com/products/2tip-1308-35681
UPDATE: Second source, 99.9% match !! http://www.ebay.com/itm/172311854193