I've had two close guesses. Time to spill the beans.
The car in question is the 2005 Roadster Coupe Trial Version, that did the rounds at the shows in Japan, before being sold on to the public. The car was intended for full production, but it seems it ended up becoming the Monocraft kit.
The car left the factory painted silver. The VIN is unusual; when the NB was launched, the first vins were NB6-100001 and NB8-100001 etc Face Lift Bs were numbers N66-200001 and so forth. So why is this one NB6-700001. Mazda sold less than 40,000 of so NB-FLs in Japan; it was a slow seller.
So that means two things; either this coupe is actually the very first 1.6 Roadster built, and thereafter lead a long life on the show circuit, in various colours. Or the VIN was a "fake", in that the car wasn't issued a VIN until late 2004, to coincide with, surprise surprise, the genuinely 700,000th model to be built, handily a US spec Miata turbo.... I think the latter.
The colour as correctly spotted by Giryan, isn't a metallic; its been described as a china blue, probably a special mix, and clearly inspired by the Gulf oil blue used on GT40s and Porsches (someone in the UK had his Boxter painted by the factory in this colour; looks superb).
The car then appeared in a showroom, for sale at 3.7 milion yen ($30kish). A bargain perhaps. Show cars like this rarely reach the public, and as a genuine one-off, it would have been so easy to import into the US.