Update: I had a nice long chat with James Dowling, and we compared notes on our individual efforts to discover when the Parachrom Blu was first introduced. He confirmed that Rolex has been telling him, like me, that any 4130 equiped Daytona has the Parachrom Blu hairspring. But James also confirmed that the blue color of the hairspring isn't caused by an oxide coating - as he understands it, the blue color is a physical property of the two elements which combine to create the Parachrom alloy under tremendous heat and pressure. The alloy turns blue as soon as it hits oxygen. So for him, it's just as big of a mystery as it is for me, and the information that Rolex is providing just doesn't make sense, based on what we know of the Parachrom manufacturing process.

Rolex USA is further researching this point, and will be getting back with me (hopefully) within the next week or so.