Aldo,
The closest I came to acceptable touchup to chromovelato Raleigh was using "Orange Anodize" Dupli-Color Metalcast from Kragen, Checker, etc. Different color of same stuff was not quite as good for Vent Noir smokey chromo but I needed more time to experiment. Use very thin light coats til best match then rubout to blend. Avoid runs/sags as they are very noticeable. Mask or use fine brush for small areas such as chips and scratches.
Jack Romans
Sacramento, CA