I tried 3 shades that were mixed in the paint shop, but the airbrush (with a 0.5mm needle) doesn't seem to let the full color through. Therefore, the shade is more silver than blue.
Dupli-Color 20-0730 performed best. Better than extra mixed. As I see from the Dupli-Color specification, it SHOULD be RAL 5004 (Black Blue)??
On the second photo on the right, you can see how silvery the mixed color works. In the first picture, the right part is painted, with Dupli-Color.