It's a custom mix. One of the fellows who participated in the Smithsonian restoration of the 11-foot FX miniature was kind enough to forward a set of paint swatches based on the original Pilot paint scheme, so the colors should be fairly accurate (or as accurate as it's possible to get at this point).
They're actually dark grey Dry Transfers. I wanted to simulate the painted-on look of the original 1st Pilot miniature. Most of the hull markings are painted on using vinyl masks (I generally try not to use decals if I can avoid it). Weathering is oils, lightly applied with make-up brushes. The surface is finished off with a satin top-coat.
Yeah, I think that took a lot of us by surprise, lol. Here’s a “roll-out” shot of the 11-footer, taken the day it was delivered to the production from Production Models in Burbank. As you can see, the dorsal is clearly blue.
https://farm5.staticflickr.com/4279/34878239004_b1c4ef6286_b.jpg11147011_1399633503698873_3150239761910290459_n by
Carson Dyle, on Flickr