Here is a blue Ameraucana:

Two copies of the diluting gene result in "splash" plumage. In chickens, splash is a very light color, pale grey or white with "splashes" of black and darker grey in the feathers, especially in the wings and tail. Here's a pretty splash Ameraucana:

When a chicken receives NO copies of the blue diluting gene, that means any black feathers remain black.
So, when a blue rooster and a blue hen reproduce, even though they're both blue, only about half of their offspring will be blue. About 25% of their offspring will be black... and the last 25% or so will be splash. PLEASE KEEP THIS IN MIND WHEN YOU ORDER! Not all of your blues will actually be blue!
So, while it's possible that with good luck you'll get all blue (or all splash, if that's your favorite), but it's just not likely, and you shouldn't count on it. Flip two coins. How many times does one come up heads and one tails? How often do you get two tails? Usually it works out to about 50-25-25 as we've described. You can see why below:

Here's Lucie, our mascot, showing off her B/B/S colors!

Because blue chicks you order can be blue, black, or splash, their down can also have subtly different colors at hatch. The chicks may appear mostly white or yellow, white/yellow with spots, blue/gray with white or yellow spots, black, blue/gray, or black with white/yellow spots.