I don't think that would work. I can't give you a specific time, but would estimate that within less than a minute in the Nitre Blue, the thin cross section of a blade's edge would be tempered beyond use. It might be worth the effort to try soaking an experimental blade of the same material in the Nitre Blue at around 400F for an extended period of time to see how that works for you. Coloring a blade is always a give-n-take situation....we're always giving up one thing to achieve another. In this case we usually give up the blade hardness in order to achieve those "cool" colors. About the only way I've found around it is the low temp for long duration soak, or the use of multiple methods on the same blade, such as a combination of Nitre Blue, heat coloring, and baking lacquers.
I've actually had collectors who demanded that the blades be hot blued, even though I repeatedly explained that the temper would be destroyed. From those experiences I've come to learn that it's all relevant to what the individual deems most important...looks or performance.