From Marshall Ketchum of Genoa, New York, and then sometime Florence, Arizona says

The glass that we now all call Blue Aurene wasn’t always called by that name in the factory. According to the factory records housed in the Rakow Library that were used by the sales dept. the general use of the term Blue Aurene didn’t begin until about the early 1920s with shape numbers in the early 6000s. Before that time Blue Aurene was called Cobalt Blue. If the records referred to Aurene they meant specifically Gold Aurene.

To add somewhat to the confusion the term Blue Aurene was used earlier for a few specific shapes. These shapes were vases 2429, 2452 through 2459 and 2461 though 2471. The latter series were also made in Green Aurene. Since the line drawings for many of these shapes show that they were decorated I suspect that the original name for these decorated shapes in what some are now calling Tiffany Blue was actually Blue Aurene.

It is not clear, to me at least, where the name Tiffany Blue comes from. It is listed in Gardner and Tom Dimitroff uses it somewhat cautiously in Fig.10.40. If you search the factory records there is exactly one reference to Tiffany Blue for shade shape 870. There are 2 references for Tiffany Green in shades 822 and 915. There are two references for Tiffany Opal in shades 896 and 2348. There are even a few references that would lead one to believe that Steuben sold glass to Tiffany. I suspect that the original name for these decorated Blue pieces was Blue Aurene and at some point the name Tiffany Blue was invented to reduce the confusion when Blue Aurene became a more general term.

Bobby Rockwell has a different set of factory records that were used in the sales dept. that I have seen but have not had the opportunity to study. They might provide more information about Tiffany Blue.