Are there no other colors visible at all if the coin is tilted in various directions under the light ? If there are, then I would say it is NT. If not, then you may well be right.
Guys, with all due respect, nickel tones all-blue all the time, and perfectly naturally. Please take a look at the 100% NT mint set here for an example of monochromatic sky-blue on a nickel. http://www.cointalk.com/forum/t47605-2/ More often you see it with some hue of "pee" yellow: But I have seen many, many NT nickels that are sky blue (although Larry's right in that they don't often come quite as even as the nickel in this thread, it does happen).
The only other colors are the bits of gold in the image. I actually had to work at catching that. It's just really blue with little if any progression in color. Any guesses on the holder it's in?